Merge branch 'master' of https://git.openprivacy.ca/cwtch.im/tapir

.drone.yml

@@ -43,7 +43,7 @@ pipeline:
     commands:
     - ./tor -f ./torrc
     - sleep 15
-    - go test -v cwtch.im/tapir/testing
+    - go test -race -v cwtch.im/tapir/testing
   notify-email:
     image: drillster/drone-email
     host: build.openprivacy.ca

.gitignore

@@ -3,3 +3,7 @@ vendor/
 /tor/
 coverage.out
 /testing/tor/
+/applications/tor/
+*.db
+/applications/tokenboard/tor/
+fuzzing/

application.go

@@ -1,7 +1,24 @@
 package tapir
 
+import (
+	"cwtch.im/tapir/primitives/core"
+)
+
+// Capability defines a status granted to a connection, from an application. That allows the connection to access
+// other Application or functions within an Application.
+type Capability string
+
 // Application defines the interface for all Tapir Applications
 type Application interface {
 	NewInstance() Application
 	Init(connection Connection)
+	Transcript() *core.Transcript
+	PropagateTranscript(transcript *core.Transcript)
+}
+
+// InteractiveApplication defines the interface for interactive Tapir applications (apps that expect the user to send
+// and receive messages from)
+type InteractiveApplication interface {
+	Application
+	Listen()
 }

applications/application_chain.go

@@ -0,0 +1,58 @@
+package applications
+
+import (
+	"cwtch.im/tapir"
+)
+
+// ApplicationChain is a meta-app that can be used to build complex applications from other applications
+type ApplicationChain struct {
+	TranscriptApp
+	apps         []tapir.Application
+	endapp       tapir.InteractiveApplication
+	capabilities []tapir.Capability
+}
+
+// ChainApplication adds a new application to the chain. Returns a pointer to app so this call
+// can itself be chained.
+func (appchain *ApplicationChain) ChainApplication(app tapir.Application, capability tapir.Capability) *ApplicationChain {
+	appchain.apps = append(appchain.apps, app.NewInstance())
+	appchain.capabilities = append(appchain.capabilities, capability)
+	return appchain
+}
+
+// ChainInteractiveApplication adds an interactive application to the chain. There can only be 1 interactive application.
+func (appchain *ApplicationChain) ChainInteractiveApplication(app tapir.InteractiveApplication) *ApplicationChain {
+	appchain.endapp = app
+	return appchain
+}
+
+// NewInstance should always return a new instantiation of the application.
+func (appchain *ApplicationChain) NewInstance() tapir.Application {
+	applicationChain := new(ApplicationChain)
+	for _, app := range appchain.apps {
+		applicationChain.apps = append(applicationChain.apps, app.NewInstance())
+	}
+	applicationChain.capabilities = appchain.capabilities
+	return applicationChain
+}
+
+// Init is run when the connection is first started.
+func (appchain *ApplicationChain) Init(connection tapir.Connection) {
+	appchain.TranscriptApp.Init(connection)
+	for i, app := range appchain.apps {
+		app.PropagateTranscript(appchain.transcript)
+		app.Init(connection)
+		if connection.HasCapability(appchain.capabilities[i]) == false {
+			connection.Close()
+			return
+		}
+		connection.SetApp(app)
+	}
+}
+
+// Listen calls listen on the Interactive application
+func (appchain *ApplicationChain) Listen() {
+	if appchain.endapp != nil {
+		appchain.endapp.Listen()
+	}
+}

applications/auth.go

@@ -17,10 +17,11 @@ type AuthMessage struct {
 }
 
 // AuthCapability defines the Authentication Capability granted by AuthApp
-const AuthCapability = "AUTH"
+const AuthCapability = tapir.Capability("AuthenticationCapability")
 
 // AuthApp is the concrete Application type that handles Authentication
 type AuthApp struct {
+	TranscriptApp
 }
 
 // NewInstance creates a new instance of the AuthApp
@@ -30,7 +31,8 @@ func (ea AuthApp) NewInstance() tapir.Application {
 
 // Init runs the entire AuthApp protocol, at the end of the protocol either the connection is granted AUTH capability
 // or the connection is closed.
-func (ea AuthApp) Init(connection tapir.Connection) {
+func (ea *AuthApp) Init(connection tapir.Connection) {
+	ea.TranscriptApp.Init(connection)
 	longTermPubKey := ed25519.PublicKey(connection.ID().PublicKeyBytes())
 	ephemeralIdentity, _ := primitives.InitializeEphemeralIdentity()
 	authMessage := AuthMessage{LongTermPublicKey: longTermPubKey, EphemeralPublicKey: ephemeralIdentity.PublicKey()}
@@ -61,7 +63,7 @@ func (ea AuthApp) Init(connection tapir.Connection) {
 	challengeRemote, _ := json.Marshal(remoteAuthMessage)
 	challengeLocal, _ := json.Marshal(authMessage)
 
-	// Define canonical labels so both sides of the
+	// Define canonical labels so both sides of the connection can generate the same key
 	var outboundAuthMessage []byte
 	var outboundHostname string
 	var inboundAuthMessage []byte
@@ -80,8 +82,10 @@ func (ea AuthApp) Init(connection tapir.Connection) {
 	}
 
 	// Derive a challenge from the transcript of the public parameters of this authentication protocol
-	var transcript *primitives.Transcript
-	transcript = primitives.NewTranscript("tapir-auth-" + outboundHostname + "-" + inboundHostname)
+	transcript := ea.Transcript()
+	transcript.NewProtocol("auth-app")
+	transcript.AddToTranscript("outbound-hostname", []byte(outboundHostname))
+	transcript.AddToTranscript("inbound-hostname", []byte(inboundHostname))
 	transcript.AddToTranscript("outbound-challenge", outboundAuthMessage)
 	transcript.AddToTranscript("inbound-challenge", inboundAuthMessage)
 	challengeBytes := transcript.CommitToTranscript("3dh-auth-challenge")
@@ -92,14 +96,16 @@ func (ea AuthApp) Init(connection tapir.Connection) {
 
 	// Since we have set the encryption key on the connection the connection will encrypt any messages we send with that key
 	// To test that the remote peer has done the same we calculate a challenge hash based on the transcript so far and send it to them
+	// along with our hostname
 	// We expect the remote to do the same, and compare the two.
 	// If successful we extend our auth capability to the connection and reassert the hostname.
 	// We note that the only successful scenario here requires that the remote peer have successfully derived the same
 	// encryption key and the same transcript challenge.
-	connection.Send(challengeBytes)
+	connection.Send(append(challengeBytes, []byte(connection.ID().Hostname())...))
 	remoteChallenge := connection.Expect()
-	if subtle.ConstantTimeCompare(challengeBytes, remoteChallenge) == 1 {
-		connection.SetHostname(utils.GetTorV3Hostname(remoteAuthMessage.LongTermPublicKey))
+	assertedHostname := utils.GetTorV3Hostname(remoteAuthMessage.LongTermPublicKey)
+	if subtle.ConstantTimeCompare(append(challengeBytes, []byte(assertedHostname)...), remoteChallenge) == 1 {
+		connection.SetHostname(assertedHostname)
 		connection.SetCapability(AuthCapability)
 	} else {
 		log.Errorf("Failed Decrypt Challenge: [%x] [%x]\n", remoteChallenge, challengeBytes)

applications/auth_test.go

@@ -47,11 +47,11 @@ func (MockConnection) SetHostname(hostname string) {
 	panic("implement me")
 }
 
-func (MockConnection) HasCapability(name string) bool {
+func (MockConnection) HasCapability(name tapir.Capability) bool {
 	panic("implement me")
 }
 
-func (MockConnection) SetCapability(name string) {
+func (MockConnection) SetCapability(name tapir.Capability) {
 	panic("implement me")
 }
 
@@ -72,6 +72,10 @@ func (MockConnection) App() tapir.Application {
 	return nil
 }
 
+func (MockConnection) SetApp(tapir.Application) {
+	// no op
+}
+
 func (MockConnection) IsClosed() bool {
 	panic("implement me")
 }

applications/proof_of_work_app.go

@@ -0,0 +1,102 @@
+package applications
+
+import (
+	"crypto/sha256"
+	"cwtch.im/tapir"
+	"cwtch.im/tapir/primitives/core"
+	"git.openprivacy.ca/openprivacy/libricochet-go/log"
+)
+
+// ProofOfWorkApplication forces the incoming connection to do proof of work before granting a capability
+type ProofOfWorkApplication struct {
+	TranscriptApp
+}
+
+// transcript constants
+const (
+	PoWApp       = "pow-app"
+	PoWSeed      = "pow-seed"
+	PoWChallenge = "pow-challenge"
+	PoWPRNG      = "pow-prng"
+	PoWSolution  = "pow-solution"
+)
+
+// SuccessfulProofOfWorkCapability is given when a successfully PoW Challenge has been Completed
+const SuccessfulProofOfWorkCapability = tapir.Capability("SuccessfulProofOfWorkCapability")
+
+// NewInstance should always return a new instantiation of the application.
+func (powapp *ProofOfWorkApplication) NewInstance() tapir.Application {
+	return new(ProofOfWorkApplication)
+}
+
+// Init is run when the connection is first started.
+func (powapp *ProofOfWorkApplication) Init(connection tapir.Connection) {
+	powapp.Transcript().NewProtocol(PoWApp)
+	if connection.IsOutbound() {
+		powapp.Transcript().AddToTranscript(PoWSeed, connection.Expect())
+		solution := powapp.solveChallenge(powapp.Transcript().CommitToTranscript(PoWChallenge), powapp.transcript.CommitToPRNG(PoWPRNG))
+		powapp.transcript.AddToTranscript(PoWSolution, solution)
+		connection.Send(solution)
+		connection.SetCapability(SuccessfulProofOfWorkCapability) // We can self grant.because the server will close the connection on failure
+		return
+	}
+
+	// We may be the first application, in which case we need to randomize the transcript challenge
+	// We use the random hostname of the inbound server (if we've authenticated them then the challenge will
+	// already be sufficiently randomized, so this doesn't hurt)
+	// It does sadly mean an additional round trip.
+	powapp.Transcript().AddToTranscript(PoWSeed, []byte(connection.Hostname()))
+	connection.Send([]byte(connection.Hostname()))
+	solution := connection.Expect()
+	challenge := powapp.Transcript().CommitToTranscript(PoWChallenge)
+	// soft-commitment to the prng, doesn't force the client to use it (but we could technically check that it did, not necessary for the security of this App)
+	powapp.transcript.CommitToPRNG(PoWPRNG)
+	powapp.transcript.AddToTranscript(PoWSolution, solution)
+	if powapp.validateChallenge(challenge, solution) {
+		connection.SetCapability(SuccessfulProofOfWorkCapability)
+		return
+	}
+}
+
+// SolveChallenge takes in a challenge and a message and returns a solution
+// The solution is a 24 byte nonce which when hashed with the challenge and the message
+// produces a sha256 hash with Difficulty leading 0s
+func (powapp *ProofOfWorkApplication) solveChallenge(challenge []byte, prng core.PRNG) []byte {
+	solved := false
+	var sum [32]byte
+	solution := []byte{}
+	solve := make([]byte, len(challenge)+32)
+	for !solved {
+
+		solution = prng.Next().Encode(nil)
+
+		copy(solve[0:], solution[:])
+		copy(solve[len(solution):], challenge[:])
+		sum = sha256.Sum256(solve)
+
+		solved = true
+		for i := 0; i < 2; i++ {
+			if sum[i] != 0x00 {
+				solved = false
+			}
+		}
+	}
+	log.Debugf("Validated Challenge %v: %v %v\n", challenge, solution, sum)
+	return solution[:]
+}
+
+// ValidateChallenge returns true if the message and spamguard pass the challenge
+func (powapp *ProofOfWorkApplication) validateChallenge(challenge []byte, solution []byte) bool {
+	solve := make([]byte, len(challenge)+32)
+	copy(solve[0:], solution[0:32])
+	copy(solve[32:], challenge[:])
+	sum := sha256.Sum256(solve)
+
+	for i := 0; i < 2; i++ {
+		if sum[i] != 0x00 {
+			return false
+		}
+	}
+	log.Debugf("Validated Challenge %v: %v %v\n", challenge, solution, sum)
+	return true
+}

applications/token_app.go

@@ -0,0 +1,64 @@
+package applications
+
+import (
+	"cwtch.im/tapir"
+	"cwtch.im/tapir/primitives/privacypass"
+	"encoding/json"
+	"git.openprivacy.ca/openprivacy/libricochet-go/log"
+)
+
+// TokenApplication provides Tokens for PoW
+type TokenApplication struct {
+	TranscriptApp
+	TokenService *privacypass.TokenServer
+	Tokens       []*privacypass.Token
+}
+
+// HasTokensCapability is granted once the client has obtained signed tokens
+const HasTokensCapability = tapir.Capability("HasTokensCapability")
+const numTokens = 10
+
+// NewInstance should always return a new instantiation of the application.
+func (tokenapp *TokenApplication) NewInstance() tapir.Application {
+	app := new(TokenApplication)
+	app.TokenService = tokenapp.TokenService
+	return app
+}
+
+// Init is run when the connection is first started.
+func (tokenapp *TokenApplication) Init(connection tapir.Connection) {
+	tokenapp.Transcript().NewProtocol("token-app")
+	log.Debugf(tokenapp.Transcript().OutputTranscriptToAudit())
+	if connection.IsOutbound() {
+		tokens, blinded := privacypass.GenerateBlindedTokenBatch(numTokens)
+		data, _ := json.Marshal(blinded)
+		connection.Send(data)
+		var signedBatch privacypass.SignedBatchWithProof
+		err := json.Unmarshal(connection.Expect(), &signedBatch)
+		if err == nil {
+			verified := privacypass.UnblindSignedTokenBatch(tokens, blinded, signedBatch.SignedTokens, tokenapp.TokenService.Y, signedBatch.Proof, tokenapp.Transcript())
+			if verified {
+				log.Debugf("Successfully obtained signed tokens")
+				tokenapp.Tokens = tokens
+				connection.SetCapability(HasTokensCapability)
+				return
+			}
+			// This will close the connection by default and no tokens will be available.
+			// This usecase can be checked by the existing WaitForCapabilityOrClose() function using the HasTokensCapability
+			// If the connection closes without the HasTokensCapability then the error can be handled by whatever client needs it
+			log.Debugf("Failed to verify signed token batch")
+		}
+		return
+	}
+
+	// We are the server
+	var blinded []privacypass.BlindedToken
+	err := json.Unmarshal(connection.Expect(), &blinded)
+	if err == nil {
+		batchProof := tokenapp.TokenService.SignBlindedTokenBatch(blinded, tokenapp.Transcript())
+		log.Debugf(tokenapp.Transcript().OutputTranscriptToAudit())
+		data, _ := json.Marshal(batchProof)
+		connection.Send(data)
+		return
+	}
+}

applications/tokenboard/client.go

@@ -0,0 +1,111 @@
+package tokenboard
+
+import (
+	"cwtch.im/tapir"
+	"cwtch.im/tapir/applications"
+	"cwtch.im/tapir/primitives/auditable"
+	"cwtch.im/tapir/primitives/privacypass"
+	"encoding/json"
+	"git.openprivacy.ca/openprivacy/libricochet-go/log"
+)
+
+// NewTokenBoardClient generates a new Client for Token Board
+func NewTokenBoardClient(store *auditable.Store, handler AppHandler, paymentHandler privacypass.TokenPaymentHandler) tapir.Application {
+	tba := new(Client)
+	tba.AuditableStore = store
+	tba.handler = handler
+	tba.paymentHandler = paymentHandler
+	return tba
+}
+
+// Client defines a client for the TokenBoard server
+type Client struct {
+	applications.AuthApp
+	connection     tapir.Connection
+	AuditableStore *auditable.Store
+	paymentHandler privacypass.TokenPaymentHandler
+	handler        AppHandler
+}
+
+// NewInstance Client a new TokenBoardApp
+func (ta *Client) NewInstance() tapir.Application {
+	tba := new(Client)
+	tba.AuditableStore = ta.AuditableStore
+	tba.handler = ta.handler
+	tba.paymentHandler = ta.paymentHandler
+	return tba
+}
+
+// Init initializes the cryptographic TokenBoardApp
+func (ta *Client) Init(connection tapir.Connection) {
+	ta.AuthApp.Init(connection)
+
+	if connection.HasCapability(applications.AuthCapability) {
+		ta.connection = connection
+		go ta.Listen()
+		return
+	}
+	connection.Close()
+}
+
+// Listen processes the messages for this application
+func (ta *Client) Listen() {
+	for {
+		log.Debugf("Client waiting...")
+		data := ta.connection.Expect()
+		if len(data) == 0 {
+			log.Debugf("Server closed the connection...")
+			return // connection is closed
+		}
+
+		var message Message
+		json.Unmarshal(data, &message)
+		switch message.MessageType {
+		case postResultMessage:
+			log.Debugf("Post result: %x", message.PostResult.Proof)
+		case replayResultMessage:
+			var state auditable.State
+			log.Debugf("Replaying %v Messages...", message.ReplayResult.NumMessages)
+			lastCommit := ta.AuditableStore.LatestCommit
+			for i := 0; i < message.ReplayResult.NumMessages; i++ {
+				message := ta.connection.Expect()
+				state.Messages = append(state.Messages, message)
+			}
+			data := ta.connection.Expect()
+			var signedProof auditable.SignedProof
+			json.Unmarshal(data, &signedProof)
+			state.SignedProof = signedProof
+			err := ta.AuditableStore.AppendState(state)
+			if err == nil {
+				log.Debugf("Successfully updated Auditable Store %v", ta.AuditableStore.LatestCommit)
+				ta.handler.HandleNewMessages(lastCommit)
+			} else {
+				log.Debugf("Error updating Auditable Store %v", err)
+			}
+		}
+	}
+}
+
+// Replay posts a Replay Message to the server.
+func (ta *Client) Replay() {
+	log.Debugf("Sending replay request for %v", ta.AuditableStore.LatestCommit)
+	data, _ := json.Marshal(Message{MessageType: replayRequestMessage, ReplayRequest: replayRequest{LastCommit: ta.AuditableStore.LatestCommit}})
+	ta.connection.Send(data)
+}
+
+// PurchaseTokens purchases the given number of tokens from the server (using the provided payment handler)
+func (ta *Client) PurchaseTokens() {
+	ta.paymentHandler.MakePayment()
+}
+
+// Post sends a Post Request to the server
+func (ta *Client) Post(message auditable.Message) bool {
+	token, err := ta.paymentHandler.NextToken(message, ta.connection.Hostname())
+	if err == nil {
+		data, _ := json.Marshal(Message{MessageType: postRequestMessage, PostRequest: postRequest{Token: token, Message: message}})
+		ta.connection.Send(data)
+		return true
+	}
+	log.Debugf("No Valid Tokens: %v", err)
+	return false
+}

applications/tokenboard/common.go

@@ -0,0 +1,52 @@
+package tokenboard
+
+import (
+	"cwtch.im/tapir/primitives/auditable"
+	"cwtch.im/tapir/primitives/privacypass"
+)
+
+// AppHandler allows clients to react to specific events.
+type AppHandler interface {
+	HandleNewMessages(previousLastCommit []byte)
+}
+
+// MessageType defines the enum for TokenBoard messages
+type messageType int
+
+const (
+	replayRequestMessage messageType = iota
+	replayResultMessage
+	postRequestMessage
+	postResultMessage
+)
+
+// Message encapsulates the application protocol
+type Message struct {
+	MessageType   messageType
+	PostRequest   postRequest   `json:",omitempty"`
+	PostResult    postResult    `json:",omitempty"`
+	ReplayRequest replayRequest `json:",omitempty"`
+	ReplayResult  replayResult  `json:",omitempty"`
+}
+
+// ReplayRequest requests a reply from the given Commit
+type replayRequest struct {
+	LastCommit []byte
+}
+
+// PostRequest requests to post the message to the board with the given token
+type postRequest struct {
+	Token   privacypass.SpentToken
+	Message auditable.Message
+}
+
+// PostResult returns the success of a given post attempt
+type postResult struct {
+	Success bool
+	Proof   auditable.SignedProof
+}
+
+// ReplayResult is sent by the server before a stream of replayed messages
+type replayResult struct {
+	NumMessages int
+}

applications/tokenboard/server.go

@@ -0,0 +1,92 @@
+package tokenboard
+
+// NOTE: This is a sketch implementation, Not suitable for production use. The real auditable store is still being designed.
+
+import (
+	"cwtch.im/tapir"
+	"cwtch.im/tapir/applications"
+	"cwtch.im/tapir/primitives/auditable"
+	"cwtch.im/tapir/primitives/privacypass"
+	"encoding/json"
+	"git.openprivacy.ca/openprivacy/libricochet-go/log"
+)
+
+// NewTokenBoardServer generates new Server for Token Board
+func NewTokenBoardServer(tokenService *privacypass.TokenServer, store *auditable.Store) tapir.Application {
+	tba := new(Server)
+	tba.TokenService = tokenService
+	tba.AuditableStore = store
+	return tba
+}
+
+// Server defines the token board server
+type Server struct {
+	applications.AuthApp
+	connection     tapir.Connection
+	TokenService   *privacypass.TokenServer
+	AuditableStore *auditable.Store
+}
+
+// NewInstance creates a new TokenBoardApp
+func (ta *Server) NewInstance() tapir.Application {
+	tba := new(Server)
+	tba.TokenService = ta.TokenService
+	tba.AuditableStore = ta.AuditableStore
+	return tba
+}
+
+// Init initializes the cryptographic TokenBoardApp
+func (ta *Server) Init(connection tapir.Connection) {
+	ta.AuthApp.Init(connection)
+
+	if connection.HasCapability(applications.AuthCapability) {
+		ta.connection = connection
+		go ta.Listen()
+		return
+	}
+	connection.Close()
+}
+
+// Listen processes the messages for this application
+func (ta *Server) Listen() {
+	for {
+		data := ta.connection.Expect()
+		if len(data) == 0 {
+			return // connection is closed
+		}
+
+		var message Message
+		json.Unmarshal(data, &message)
+
+		switch message.MessageType {
+		case postRequestMessage:
+			postrequest := message.PostRequest
+			log.Debugf("Received a Post Message Request: %x %x", postrequest.Token, postrequest.Message)
+			ta.postMessageRequest(postrequest.Token, postrequest.Message)
+		case replayRequestMessage:
+			log.Debugf("Received Replay Request %v", message.ReplayRequest)
+			state := ta.AuditableStore.GetStateAfter(message.ReplayRequest.LastCommit)
+			response, _ := json.Marshal(Message{MessageType: replayResultMessage, ReplayResult: replayResult{len(state.Messages)}})
+			log.Debugf("Sending Replay Response %v", replayResult{len(state.Messages)})
+			ta.connection.Send(response)
+			for _, message := range state.Messages {
+				ta.connection.Send(message)
+			}
+			data, _ := json.Marshal(state.SignedProof)
+			ta.connection.Send(data)
+		}
+	}
+}
+
+func (ta *Server) postMessageRequest(token privacypass.SpentToken, message auditable.Message) {
+	if err := ta.TokenService.SpendToken(token, append(message, ta.connection.ID().Hostname()...)); err == nil {
+		log.Debugf("Token is valid")
+		signedproof := ta.AuditableStore.Add(message)
+		data, _ := json.Marshal(Message{MessageType: postResultMessage, PostResult: postResult{true, signedproof}})
+		ta.connection.Send(data)
+	} else {
+		log.Debugf("Attempt to spend an invalid token: %v", err)
+		data, _ := json.Marshal(Message{MessageType: postResultMessage, PostResult: postResult{false, auditable.SignedProof{}}})
+		ta.connection.Send(data)
+	}
+}

applications/tokenboard/tokenboard_integration_test.go

@@ -0,0 +1,152 @@
+package tokenboard
+
+import (
+	"cwtch.im/tapir"
+	"cwtch.im/tapir/applications"
+	"cwtch.im/tapir/networks/tor"
+	"cwtch.im/tapir/primitives"
+	"cwtch.im/tapir/primitives/auditable"
+	"cwtch.im/tapir/primitives/privacypass"
+	"errors"
+	"git.openprivacy.ca/openprivacy/libricochet-go/connectivity"
+	"git.openprivacy.ca/openprivacy/libricochet-go/log"
+	"runtime"
+	"sync"
+	"testing"
+	"time"
+)
+
+type Handler struct {
+	Store *auditable.Store
+}
+
+func (h Handler) HandleNewMessages(previousLastCommit []byte) {
+	log.Debugf("Handling Messages After %x", previousLastCommit)
+	messages := h.Store.GetMessagesAfter(previousLastCommit)
+	for _, message := range messages {
+		log.Debugf("Message %s", message)
+	}
+}
+
+type FreePaymentHandler struct {
+	tokens         []*privacypass.Token
+	TokenService   *privacypass.TokenServer
+	ACN            connectivity.ACN
+	ServerHostname string
+}
+
+func (fph *FreePaymentHandler) MakePayment() {
+	id, sk := primitives.InitializeEphemeralIdentity()
+	var client tapir.Service
+	client = new(tor.BaseOnionService)
+	client.Init(fph.ACN, sk, &id)
+
+	tokenApplication := new(applications.TokenApplication)
+	tokenApplication.TokenService = fph.TokenService
+	powTokenApp := new(applications.ApplicationChain).
+		ChainApplication(new(applications.ProofOfWorkApplication), applications.SuccessfulProofOfWorkCapability).
+		ChainApplication(tokenApplication, applications.HasTokensCapability)
+	client.Connect(fph.ServerHostname, powTokenApp)
+	conn, err := client.WaitForCapabilityOrClose(fph.ServerHostname, applications.HasTokensCapability)
+	if err == nil {
+		powtapp, _ := conn.App().(*applications.TokenApplication)
+		fph.tokens = append(fph.tokens, powtapp.Tokens...)
+		log.Debugf("Transcript: %v", powtapp.Transcript().OutputTranscriptToAudit())
+		conn.Close()
+		return
+	}
+	log.Debugf("Error making payment: %v", err)
+}
+
+func (fph *FreePaymentHandler) NextToken(data []byte, hostname string) (privacypass.SpentToken, error) {
+	if len(fph.tokens) == 0 {
+		return privacypass.SpentToken{}, errors.New("No more tokens")
+	}
+	token := fph.tokens[0]
+	fph.tokens = fph.tokens[1:]
+	return token.SpendToken(append(data, hostname...)), nil
+}
+
+func TestTokenBoardApp(t *testing.T) {
+	//	numRoutinesStart := runtime.NumGoroutine()
+	log.SetLevel(log.LevelDebug)
+	log.Infof("Number of goroutines open at start: %d", runtime.NumGoroutine())
+	// Connect to Tor
+	var acn connectivity.ACN
+	acn, _ = connectivity.StartTor("./", "")
+	acn.WaitTillBootstrapped()
+
+	// Generate Server Key
+	sid, sk := primitives.InitializeEphemeralIdentity()
+	tokenService := privacypass.NewTokenServer()
+	serverAuditableStore := new(auditable.Store)
+	serverAuditableStore.Init(sid)
+
+	clientAuditableStore := new(auditable.Store)
+	// Only initialize with public parameters
+	sidpubk := sid.PublicKey()
+	publicsid := primitives.InitializeIdentity("server", nil, &sidpubk)
+	clientAuditableStore.Init(publicsid)
+
+	// Init the Server running the Simple App.
+	var service tapir.Service
+	service = new(tor.BaseOnionService)
+	service.Init(acn, sk, &sid)
+
+	// Goroutine Management
+	sg := new(sync.WaitGroup)
+	sg.Add(1)
+	go func() {
+		service.Listen(NewTokenBoardServer(tokenService, serverAuditableStore))
+		sg.Done()
+	}()
+
+	// Init the Server running the PoW Token App.
+	var powTokenService tapir.Service
+	powTokenService = new(tor.BaseOnionService)
+	spowid, spowk := primitives.InitializeEphemeralIdentity()
+	powTokenService.Init(acn, spowk, &spowid)
+	sg.Add(1)
+	go func() {
+		tokenApplication := new(applications.TokenApplication)
+		tokenApplication.TokenService = tokenService
+		powTokenApp := new(applications.ApplicationChain).
+			ChainApplication(new(applications.ProofOfWorkApplication), applications.SuccessfulProofOfWorkCapability).
+			ChainApplication(tokenApplication, applications.HasTokensCapability)
+		powTokenService.Listen(powTokenApp)
+		sg.Done()
+	}()
+
+	time.Sleep(time.Second * 60) // wait for server to initialize
+	id, sk := primitives.InitializeEphemeralIdentity()
+	var client tapir.Service
+	client = new(tor.BaseOnionService)
+	client.Init(acn, sk, &id)
+	client.Connect(sid.Hostname(), NewTokenBoardClient(clientAuditableStore, Handler{Store: clientAuditableStore}, &FreePaymentHandler{ACN: acn, TokenService: tokenService, ServerHostname: spowid.Hostname()}))
+	client.WaitForCapabilityOrClose(sid.Hostname(), applications.AuthCapability)
+	conn, _ := client.GetConnection(sid.Hostname())
+	tba, _ := conn.App().(*Client)
+	tba.PurchaseTokens()
+	tba.Post([]byte("HELLO 1"))
+	tba.Post([]byte("HELLO 2"))
+	tba.Post([]byte("HELLO 3"))
+	tba.Post([]byte("HELLO 4"))
+	tba.Post([]byte("HELLO 5"))
+	tba.Replay()
+	time.Sleep(time.Second * 10) // We have to wait for the async replay request!
+	tba.Post([]byte("HELLO 6"))
+	tba.Post([]byte("HELLO 7"))
+	tba.Post([]byte("HELLO 8"))
+	tba.Post([]byte("HELLO 9"))
+	tba.Post([]byte("HELLO 10"))
+	tba.Replay()
+	time.Sleep(time.Second * 10) // We have to wait for the async replay request!
+
+	if tba.Post([]byte("HELLO 11")) {
+		t.Errorf("Post should have failed.")
+	}
+
+	time.Sleep(time.Second * 10)
+	acn.Close()
+	sg.Wait()
+}

applications/transcript_app.go

@@ -0,0 +1,32 @@
+package applications
+
+import (
+	"cwtch.im/tapir"
+	"cwtch.im/tapir/primitives/core"
+)
+
+// TranscriptApp defines a Tapir Meta-App which provides a global cryptographic transcript
+type TranscriptApp struct {
+	transcript *core.Transcript
+}
+
+// NewInstance creates a new TranscriptApp
+func (TranscriptApp) NewInstance() tapir.Application {
+	ta := new(TranscriptApp)
+	return ta
+}
+
+// Init initializes the cryptographic transcript
+func (ta *TranscriptApp) Init(connection tapir.Connection) {
+	ta.transcript = core.NewTranscript("tapir-transcript")
+}
+
+// Transcript returns a pointer to the cryptographic transcript
+func (ta *TranscriptApp) Transcript() *core.Transcript {
+	return ta.transcript
+}
+
+// PropagateTranscript overrides the default transcript and propagates a transcript from a previous session
+func (ta *TranscriptApp) PropagateTranscript(transcript *core.Transcript) {
+	ta.transcript = transcript
+}

go.mod

@@ -2,5 +2,11 @@ module cwtch.im/tapir
 
 require (
 	git.openprivacy.ca/openprivacy/libricochet-go v1.0.4
+	github.com/gtank/merlin v0.1.1
+	github.com/gtank/ristretto255 v0.1.2
+	go.etcd.io/bbolt v1.3.3
 	golang.org/x/crypto v0.0.0-20190513172903-22d7a77e9e5f
+	golang.org/x/sync v0.0.0-20190423024810-112230192c58 // indirect
 )
+
+go 1.13

go.sum

@@ -8,11 +8,19 @@ github.com/davecgh/go-spew v1.1.0 h1:ZDRjVQ15GmhC3fiQ8ni8+OwkZQO4DARzQgrnXU1Liz8
 github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/golang/protobuf v1.2.0 h1:P3YflyNX/ehuJFLhxviNdFxQPkGK5cDcApsge1SqnvM=
 github.com/golang/protobuf v1.2.0/go.mod h1:6lQm79b+lXiMfvg/cZm0SGofjICqVBUtrP5yJMmIC1U=
+github.com/gtank/merlin v0.1.1 h1:eQ90iG7K9pOhtereWsmyRJ6RAwcP4tHTDBHXNg+u5is=
+github.com/gtank/merlin v0.1.1/go.mod h1:T86dnYJhcGOh5BjZFCJWTDeTK7XW8uE+E21Cy/bIQ+s=
+github.com/gtank/ristretto255 v0.1.2 h1:JEqUCPA1NvLq5DwYtuzigd7ss8fwbYay9fi4/5uMzcc=
+github.com/gtank/ristretto255 v0.1.2/go.mod h1:Ph5OpO6c7xKUGROZfWVLiJf9icMDwUeIvY4OmlYW69o=
+github.com/mimoo/StrobeGo v0.0.0-20181016162300-f8f6d4d2b643 h1:hLDRPB66XQT/8+wG9WsDpiCvZf1yKO7sz7scAjSlBa0=
+github.com/mimoo/StrobeGo v0.0.0-20181016162300-f8f6d4d2b643/go.mod h1:43+3pMjjKimDBf5Kr4ZFNGbLql1zKkbImw+fZbw3geM=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
 github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
 github.com/stretchr/testify v1.3.0 h1:TivCn/peBQ7UY8ooIcPgZFpTNSz0Q2U6UrFlUfqbe0Q=
 github.com/stretchr/testify v1.3.0/go.mod h1:M5WIy9Dh21IEIfnGCwXGc5bZfKNJtfHm1UVUgZn+9EI=
+go.etcd.io/bbolt v1.3.3 h1:MUGmc65QhB3pIlaQ5bB4LwqSj6GIonVJXpZiaKNyaKk=
+go.etcd.io/bbolt v1.3.3/go.mod h1:IbVyRI1SCnLcuJnV2u8VeU0CEYM7e686BmAb1XKL+uU=
 golang.org/x/crypto v0.0.0-20190128193316-c7b33c32a30b/go.mod h1:6SG95UA2DQfeDnfUPMdvaQW0Q7yPrPDi9nlGo2tz2b4=
 golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
 golang.org/x/crypto v0.0.0-20190513172903-22d7a77e9e5f h1:R423Cnkcp5JABoeemiGEPlt9tHXFfw5kvc0yqlxRPWo=
@@ -20,8 +28,9 @@ golang.org/x/crypto v0.0.0-20190513172903-22d7a77e9e5f/go.mod h1:yigFU9vqHzYiE8U
 golang.org/x/net v0.0.0-20190125091013-d26f9f9a57f3/go.mod h1:mL1N/T3taQHkDXs73rZJwtUhF3w3ftmwwsq0BUmARs4=
 golang.org/x/net v0.0.0-20190404232315-eb5bcb51f2a3 h1:0GoQqolDA55aaLxZyTzK/Y2ePZzZTUrRacwib7cNsYQ=
 golang.org/x/net v0.0.0-20190404232315-eb5bcb51f2a3/go.mod h1:t9HGtf8HONx5eT2rtn7q6eTqICYqUVnKs3thJo3Qplg=
-golang.org/x/sync v0.0.0-20181221193216-37e7f081c4d4 h1:YUO/7uOKsKeq9UokNS62b8FYywz3ker1l1vDZRCRefw=
 golang.org/x/sync v0.0.0-20181221193216-37e7f081c4d4/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
+golang.org/x/sync v0.0.0-20190423024810-112230192c58 h1:8gQV6CLnAEikrhgkHFbMAEhagSSnXWGV915qUMm9mrU=
+golang.org/x/sync v0.0.0-20190423024810-112230192c58/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/sys v0.0.0-20190412213103-97732733099d h1:+R4KGOnez64A81RvjARKc4UT5/tI9ujCIVX+P5KiHuI=
 golang.org/x/sys v0.0.0-20190412213103-97732733099d/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=

networks/tor/BaseOnionService.go

@@ -34,7 +34,7 @@ func (s *BaseOnionService) Init(acn connectivity.ACN, sk ed25519.PrivateKey, id
 
 // WaitForCapabilityOrClose blocks until the connection has the given capability or the underlying connection is closed
 // (through error or user action)
-func (s *BaseOnionService) WaitForCapabilityOrClose(cid string, name string) (tapir.Connection, error) {
+func (s *BaseOnionService) WaitForCapabilityOrClose(cid string, name tapir.Capability) (tapir.Connection, error) {
 	conn, err := s.GetConnection(cid)
 	if err == nil {
 		for {
@@ -54,7 +54,6 @@ func (s *BaseOnionService) WaitForCapabilityOrClose(cid string, name string) (ta
 func (s *BaseOnionService) GetConnection(hostname string) (tapir.Connection, error) {
 	var conn tapir.Connection
 	s.connections.Range(func(key, value interface{}) bool {
-		log.Debugf("Checking %v", key)
 		connection := value.(tapir.Connection)
 		if connection.Hostname() == hostname {
 			if !connection.IsClosed() {

persistence/bolt_persistence.go

@@ -0,0 +1,77 @@
+package persistence
+
+import (
+	"encoding/json"
+	"git.openprivacy.ca/openprivacy/libricochet-go/log"
+	bolt "go.etcd.io/bbolt"
+)
+
+// BoltPersistence creates a persistence services backed by an on-disk bolt database
+type BoltPersistence struct {
+	db *bolt.DB
+}
+
+// Open opens a database
+func (bp *BoltPersistence) Open(handle string) error {
+	db, err := bolt.Open(handle, 0600, nil)
+	bp.db = db
+	log.Debugf("Loaded the Database")
+	return err
+}
+
+// Setup initializes the given buckets if they do not exist in the database
+func (bp *BoltPersistence) Setup(buckets []string) error {
+	return bp.db.Update(func(tx *bolt.Tx) error {
+		for _, bucket := range buckets {
+			tx.CreateBucketIfNotExists([]byte(bucket))
+		}
+		return nil
+	})
+}
+
+// Close closes the databases
+func (bp *BoltPersistence) Close() {
+	bp.db.Close()
+}
+
+// Persist stores a record in the database
+func (bp *BoltPersistence) Persist(bucket string, name string, value interface{}) error {
+	valueBytes, _ := json.Marshal(value)
+	return bp.db.Update(func(tx *bolt.Tx) error {
+		b := tx.Bucket([]byte(bucket))
+		b.Put([]byte(name), valueBytes)
+		return nil
+	})
+}
+
+// Check returns true if the record exists in the given bucket.
+func (bp *BoltPersistence) Check(bucket string, name string) (bool, error) {
+	log.Debugf("Checking database: %v %v", bucket, name)
+	var val []byte
+	err := bp.db.View(func(tx *bolt.Tx) error {
+		b := tx.Bucket([]byte(bucket))
+		val = b.Get([]byte(name))
+		return nil
+	})
+
+	if err != nil {
+		return false, err
+	} else if val != nil {
+		return true, nil
+	}
+	return false, nil
+}
+
+// Load reads a value from a given bucket.
+func (bp *BoltPersistence) Load(bucket string, name string, value interface{}) error {
+	var val []byte
+	err := bp.db.View(func(tx *bolt.Tx) error {
+		b := tx.Bucket([]byte(bucket))
+		val = b.Get([]byte(name))
+		return nil
+	})
+	if err != nil {
+		return err
+	}
+	return json.Unmarshal(val, &value)
+}

persistence/bolt_persistence_test.go

@@ -0,0 +1,23 @@
+package persistence
+
+import (
+	"testing"
+)
+
+func TestBoltPersistence_Open(t *testing.T) {
+	var db Service
+	db = new(BoltPersistence)
+	db.Open("test.dbgi")
+	db.Setup([]string{"tokens"})
+	db.Persist("tokens", "random_value", true)
+
+	var exists bool
+	db.Load("tokens", "random_value", &exists)
+
+	if exists {
+		t.Logf("Successfully stored: %v", exists)
+	} else {
+		t.Fatalf("Failure to store record in DB!")
+	}
+	db.Close()
+}

persistence/persistence.go

@@ -0,0 +1,11 @@
+package persistence
+
+// Service provides a consistent interface for interacting with on-disk, in-memory or server-backed storage
+type Service interface {
+	Open(handle string) error
+	Setup(buckets []string) error
+	Persist(bucket string, name string, value interface{}) error
+	Check(bucket string, name string) (bool, error)
+	Load(bucket string, name string, value interface{}) error
+	Close()
+}

primitives/auditable/auditablestore.go

@@ -0,0 +1,187 @@
+package auditable
+
+// WARNING NOTE: This is a sketch implementation, Not suitable for production use. The real auditable store is still being designed.
+
+import (
+	"cwtch.im/tapir/persistence"
+	"cwtch.im/tapir/primitives"
+	"cwtch.im/tapir/primitives/core"
+	"encoding/base64"
+	"errors"
+	"git.openprivacy.ca/openprivacy/libricochet-go/log"
+	"golang.org/x/crypto/ed25519"
+	"sync"
+)
+
+// SignedProof encapsulates a signed proof
+type SignedProof []byte
+
+// Message encapsulates a message for more readable code.
+type Message []byte
+
+// State defines an array of messages.
+type State struct {
+	SignedProof SignedProof
+	Messages    []Message
+}
+
+//
+const (
+	auditableDataStoreProtocol = "auditable-data-store"
+	newMessage                 = "new-message"
+	commit                     = "commit"
+	collapse                   = "collapse"
+)
+
+// Store defines a cryptographically secure & auditable transcript of messages sent from multiple
+// unrelated clients to a server.
+type Store struct {
+	state        State
+	identity     primitives.Identity
+	transcript   *core.Transcript
+	LatestCommit []byte
+	commits      map[string]int
+	mutex        sync.Mutex
+	db           persistence.Service
+}
+
+// Init initializes an auditable store
+func (as *Store) Init(identity primitives.Identity) {
+	as.identity = identity
+	as.transcript = core.NewTranscript(auditableDataStoreProtocol)
+	as.commits = make(map[string]int)
+}
+
+const messageBucket = "auditable-messages"
+
+// LoadFromStorage initializes an auditable store from a DB
+func (as *Store) LoadFromStorage(db persistence.Service) {
+	db.Setup([]string{messageBucket})
+	var messages []Message
+	db.Load(messageBucket, "messages", &messages)
+	log.Debugf("Loaded from Database: %v", len(messages))
+	for _, message := range messages {
+		as.add(message)
+	}
+	log.Debugf("Loaded %v Messages from the Database", len(messages))
+	as.db = db
+}
+
+// Add adds a message to the auditable store
+func (as *Store) Add(message Message) SignedProof {
+	sp := as.add(message)
+	if as.db != nil {
+		as.db.Persist(messageBucket, "messages", as.state.Messages)
+	}
+	return sp
+}
+
+// Add adds a message to the auditable store
+func (as *Store) add(message Message) SignedProof {
+	as.mutex.Lock()
+	defer as.mutex.Unlock()
+	as.transcript.AddToTranscript(newMessage, message)
+	as.LatestCommit = as.transcript.CommitToTranscript(commit)
+
+	as.state.Messages = append(as.state.Messages, message)
+	as.state.SignedProof = as.identity.Sign(as.LatestCommit)
+
+	as.commits[base64.StdEncoding.EncodeToString(as.LatestCommit)] = len(as.state.Messages) - 1
+	return as.state.SignedProof
+}
+
+// GetState returns the current auditable state
+func (as *Store) GetState() State {
+	as.mutex.Lock()
+	defer as.mutex.Unlock()
+	return as.state
+}
+
+// GetStateAfter returns the current auditable state after a given commitment
+func (as *Store) GetStateAfter(commitment []byte) State {
+	if commitment == nil {
+		return as.GetState()
+	}
+	var state State
+	state.Messages = as.GetMessagesAfter(commitment)
+	state.SignedProof = as.identity.Sign(as.LatestCommit)
+	return state
+}
+
+// GetMessagesAfter provides access to messages after the given commit.
+func (as *Store) GetMessagesAfter(latestCommit []byte) []Message {
+	as.mutex.Lock()
+	defer as.mutex.Unlock()
+	index, ok := as.commits[base64.StdEncoding.EncodeToString(latestCommit)]
+	if !ok && len(latestCommit) == 32 {
+		return []Message{}
+	} else if len(latestCommit) == 0 {
+		index = -1
+	}
+	return as.state.Messages[index+1:]
+}
+
+// AppendState merges a given state onto our state, first verifying that the two transcripts align
+func (as *Store) AppendState(state State) error {
+	next := len(as.state.Messages)
+	for i, m := range state.Messages {
+		as.state.Messages = append(as.state.Messages, m)
+
+		// We reconstruct the transcript
+		as.transcript.AddToTranscript(newMessage, m)
+		as.LatestCommit = as.transcript.CommitToTranscript(commit)
+		log.Debugf("Adding message %d commit: %x", next+i, as.LatestCommit)
+		as.commits[base64.StdEncoding.EncodeToString(as.LatestCommit)] = next + i
+	}
+
+	// verify that our state matches the servers signed state
+	// this is *not* a security check, as a rogue server can simply sign any state
+	// however committing to a state allows us to build fraud proofs for malicious servers later on.
+	if ed25519.Verify(as.identity.PublicKey(), as.LatestCommit, state.SignedProof) == false {
+		return errors.New("state is not consistent, the server is malicious")
+	}
+	return nil
+}
+
+// MergeState merges a given state onto our state, first verifying that the two transcripts align
+func (as *Store) MergeState(state State) error {
+	return as.AppendState(State{Messages: state.Messages[len(as.state.Messages):], SignedProof: state.SignedProof})
+}
+
+// VerifyFraudProof  - the main idea behind this is as follows:
+//
+// Every update requires the server to sign, and thus commit to, a transcript
+// Clients reconstruct the transcript via MergeState, as such clients can keep track of every commit.
+// if a client can present a signed transcript commit from the server that other clients do not have, it is proof
+// that either 1) they are out of sync with the server or 2) the server is presenting different transcripts to different people
+//
+// If, after syncing, the FraudProof still validates, then the server must be malicious.
+// the information revealed by publicizing a fraud proof is minimal it only reveals the inconsistent transcript commit
+// and not the cause (which could be reordered messages, dropped messages, additional messages or any combination)
+func (as *Store) VerifyFraudProof(fraudCommit []byte, signedFraudProof SignedProof, key ed25519.PublicKey) (bool, error) {
+
+	if ed25519.Verify(key, fraudCommit, signedFraudProof) == false {
+		// This could happen due to misuse of this function (trying to verify a proof with the wrong public key)
+		// This could happen if the server lies to us and submits a fake state proof, however we cannot use this to
+		// prove that the server is acting maliciously
+		return false, errors.New("signed proof has not been signed by the given public key")
+	}
+
+	_, exists := as.commits[base64.StdEncoding.EncodeToString(fraudCommit)]
+	if !exists {
+		// We have a message signed by the server which verifies that a message was inserted into the state at a given index
+		// However this directly contradicts our version of the state.
+		// There is still a possibility that we are out of sync with the server and that new messages have since been added
+		// We assume that the caller has first Merged the most recent state.
+		return true, nil
+	}
+
+	return false, nil
+}
+
+// Collapse constructs a verifiable proof stating that the server has collapsed the previous history into the current
+// root = H(onion)
+// L = H(Sign(LatestCommit))
+func (as *Store) Collapse() {
+	as.LatestCommit = as.identity.Sign(as.transcript.CommitToTranscript(collapse))
+}

primitives/auditable/auditablestore_test.go

@@ -0,0 +1,70 @@
+package auditable
+
+import (
+	"cwtch.im/tapir/persistence"
+	"cwtch.im/tapir/primitives"
+	"fmt"
+	"git.openprivacy.ca/openprivacy/libricochet-go/log"
+	"os"
+	"testing"
+)
+
+func BenchmarkAuditableStore(b *testing.B) {
+	log.SetLevel(log.LevelDebug)
+	os.Remove("benchmark-auditablestore.db")
+
+	as := new(Store)
+	serverID, _ := primitives.InitializeEphemeralIdentity()
+	as.Init(serverID)
+
+	db := new(persistence.BoltPersistence)
+	db.Open("benchmark-auditablestore.db")
+
+	as.LoadFromStorage(db)
+
+	for i := 0; i < b.N; i++ {
+		data := fmt.Sprintf("Message %v", i)
+		as.Add(Message(data))
+	}
+	db.Close()
+	db.Open("benchmark-auditablestore.db")
+	vs := new(Store)
+	vs.Init(serverID)
+	vs.LoadFromStorage(db)
+	db.Close()
+	os.Remove("benchmark-auditablestore.db")
+}
+
+func TestAuditableStore(t *testing.T) {
+	as := new(Store)
+	vs := new(Store)
+
+	serverID, _ := primitives.InitializeEphemeralIdentity()
+	as.Init(serverID)
+	vs.Init(serverID) // This doesn't do anything
+
+	as.Add([]byte("Hello World"))
+	state := as.GetState()
+
+	if vs.MergeState(state) != nil {
+		t.Fatalf("Fraud Proof Failed on Honest Proof")
+	}
+
+	fraudProof := as.Add([]byte("Hello World 2"))
+
+	// If you comment these out it simulates a lying server.
+	state = as.GetState()
+	if vs.MergeState(state) != nil {
+		t.Fatalf("Fraud Proof Failed on Honest Proof")
+	}
+
+	fraud, err := vs.VerifyFraudProof(as.LatestCommit, fraudProof, serverID.PublicKey())
+
+	if err != nil {
+		t.Fatalf("Error validated fraud proof: %v", err)
+	}
+
+	if fraud {
+		t.Fatalf("Technically a fraud, but the client hasn't updated yet")
+	}
+}

primitives/bloom.go

@@ -1,62 +0,0 @@
-package primitives
-
-import (
-	"crypto/sha256"
-	"sync"
-)
-
-// BloomFilter implements a bloom filter
-type BloomFilter struct {
-	B    []bool
-	lock sync.Mutex
-}
-
-// Init constructs a bloom filter of size m
-func (bf *BloomFilter) Init(m int16) {
-	bf.B = make([]bool, m)
-}
-
-// Hash transforms a message to a set of bit flips
-// Supports up to m == 65535
-func (bf *BloomFilter) Hash(msg []byte) []int {
-	hash := sha256.Sum256(msg)
-
-	pos1a := (int(hash[0]) + int(hash[1]) + int(hash[2]) + int(hash[3])) % 0xFF
-	pos1b := (int(hash[4]) + int(hash[5]) + int(hash[6]) + int(hash[7])) % 0xFF
-	pos1 := ((pos1a << 8) + pos1b) & (0xFFFF % len(bf.B))
-
-	pos2a := (int(hash[8]) + int(hash[9]) + int(hash[10]) + int(hash[11])) % 0xFF
-	pos2b := (int(hash[12]) + int(hash[13]) + int(hash[14]) + int(hash[15])) % 0xFF
-	pos2 := ((pos2a << 8) + pos2b) & (0xFFFF % len(bf.B))
-
-	pos3a := (int(hash[16]) + int(hash[17]) + int(hash[18]) + int(hash[19])) % 0xFF
-	pos3b := (int(hash[20]) + int(hash[21]) + int(hash[22]) + int(hash[23])) % 0xFF
-	pos3 := ((pos3a << 8) + pos3b) & (0xFFFF % len(bf.B))
-
-	pos4a := (int(hash[24]) + int(hash[25]) + int(hash[26]) + int(hash[27])) % 0xFF
-	pos4b := (int(hash[28]) + int(hash[29]) + int(hash[30]) + int(hash[31])) % 0xFF
-	pos4 := ((pos4a << 8) + pos4b) & (0xFFFF % len(bf.B))
-
-	return []int{pos1, pos2, pos3, pos4}
-}
-
-// Insert updates the BloomFilter (suitable for concurrent use)
-func (bf *BloomFilter) Insert(msg []byte) {
-	pos := bf.Hash(msg)
-	bf.lock.Lock()
-	defer bf.lock.Unlock()
-	bf.B[pos[0]] = true
-	bf.B[pos[1]] = true
-	bf.B[pos[2]] = true
-	bf.B[pos[3]] = true
-}
-
-// Check returns true if the messages might be in the BloomFilter
-// (No false positives, possible false negatives due to the probabilistic nature of the filter)
-func (bf *BloomFilter) Check(msg []byte) bool {
-	pos := bf.Hash(msg)
-	if bf.B[pos[0]] && bf.B[pos[1]] && bf.B[pos[2]] && bf.B[pos[3]] {
-		return true
-	}
-	return false
-}

primitives/core/transcript.go

@@ -0,0 +1,106 @@
+package core
+
+import (
+	"fmt"
+	"github.com/gtank/merlin"
+	ristretto "github.com/gtank/ristretto255"
+	"golang.org/x/crypto/sha3"
+	"io"
+)
+
+// Transcript provides a consistent transcript primitive for our protocols
+//
+// We have the following goals:
+//  - Allow sequential proofs over a common transcript (ensuring a single proof cannot be extracted standalone)
+//  - be able to produce a human-readable transcript for auditing.
+//
+// The design of this API was inspired by Merlin: https://docs.rs/crate/merlin/
+type Transcript struct {
+	merlinTranscript *merlin.Transcript
+	transcript       string
+}
+
+// NewTranscript creates a new Transcript with the given Label, the label should be unique to the application
+func NewTranscript(label string) *Transcript {
+	transcript := new(Transcript)
+	transcript.merlinTranscript = merlin.NewTranscript(label)
+	return transcript
+}
+
+// AddToTranscript appends a value to the transcript with the given label
+// This binds the given data to the label.
+func (t *Transcript) AddToTranscript(label string, b []byte) {
+	op := fmt.Sprintf("%s (%d) %x;", label, len(b), b)
+	t.transcript = fmt.Sprintf("%v\n%v", t.transcript, op)
+	t.merlinTranscript.AppendMessage([]byte(label), b)
+}
+
+// AddElementToTranscript appends a value to the transcript with the given label
+// This binds the given data to the label.
+func (t *Transcript) AddElementToTranscript(label string, element *ristretto.Element) {
+	t.AddToTranscript(label, element.Encode([]byte{}))
+}
+
+// OutputTranscriptToAudit outputs a human-readable copy of the transcript so far.
+func (t Transcript) OutputTranscriptToAudit() string {
+	return t.transcript
+}
+
+// NewProtocol provides explicit protocol separation in a transcript (more readable audit scripts and even more explicit
+// binding of committed values to a given context)
+func (t *Transcript) NewProtocol(label string) {
+	op := fmt.Sprintf("---- new-protcol: %s ----", label)
+	t.transcript = fmt.Sprintf("%v\n%v", t.transcript, op)
+	t.merlinTranscript.AppendMessage([]byte("protocol"), []byte(label))
+}
+
+// CommitToTranscript generates a challenge based on the current transcript, it also commits the challenge to the transcript.
+func (t *Transcript) CommitToTranscript(label string) []byte {
+	b := t.merlinTranscript.ExtractBytes([]byte(label), 64)
+	t.transcript = fmt.Sprintf("%v\nextract %v: %v", t.transcript, label, b)
+	return b
+}
+
+// PRNG defines a psuedorandom number generator
+type PRNG struct {
+	prng io.Reader
+}
+
+// Next returns the next "random" scalar from the PRNG
+func (prng *PRNG) Next() *ristretto.Scalar {
+	buf := [64]byte{}
+	io.ReadFull(prng.prng, buf[:])
+	next := new(ristretto.Scalar)
+	next.FromUniformBytes(buf[:])
+	return next
+}
+
+// CommitToPRNG commits the label to the transcript and derives a PRNG from the transcript.
+func (t *Transcript) CommitToPRNG(label string) PRNG {
+	b := t.merlinTranscript.ExtractBytes([]byte(label), 64)
+	prng := sha3.NewShake256()
+	prng.Write(b)
+	return PRNG{prng: prng}
+}
+
+// CommitToGenerator derives a verifiably random generator from the transcript
+func (t *Transcript) CommitToGenerator(label string) *ristretto.Element {
+	c := t.CommitToTranscript(label)
+	return new(ristretto.Element).FromUniformBytes(c)
+}
+
+// CommitToGenerators derives a set of verifiably random generators from the transcript
+func (t *Transcript) CommitToGenerators(label string, n int) (generators []*ristretto.Element) {
+	for i := 0; i < n; i++ {
+		generators = append(generators, t.CommitToGenerator(fmt.Sprintf("%v-%d", label, i)))
+	}
+	return generators
+}
+
+// CommitToTranscriptScalar is a convenience method for CommitToTranscript which returns a ristretto Scalar
+func (t *Transcript) CommitToTranscriptScalar(label string) *ristretto.Scalar {
+	c := t.CommitToTranscript(label)
+	s := new(ristretto.Scalar)
+	s.FromUniformBytes(c[:])
+	return s
+}

primitives/core/transcript_test.go

@@ -0,0 +1,28 @@
+package core
+
+import (
+	"testing"
+)
+
+func TestNewTranscript(t *testing.T) {
+
+	// Some very basic integrity checking
+	transcript := NewTranscript("label")
+
+	transcript.AddToTranscript("action", []byte("test data"))
+
+	if transcript.OutputTranscriptToAudit() != transcript.OutputTranscriptToAudit() {
+		t.Fatalf("Multiple Audit Calls should not impact underlying Transcript")
+	}
+	t.Logf("%v", transcript.OutputTranscriptToAudit())
+	t.Logf("%v", transcript.CommitToTranscript("first commit"))
+	t.Logf("%v", transcript.OutputTranscriptToAudit())
+	t.Logf("%v", transcript.CommitToTranscript("second commit"))
+	t.Logf("%v", transcript.OutputTranscriptToAudit())
+
+	transcript.AddToTranscript("action", []byte("test data"))
+
+	t.Logf("%v", transcript.CommitToTranscript("third commit"))
+	t.Logf("%v", transcript.OutputTranscriptToAudit())
+
+}

primitives/identity.go

@@ -41,7 +41,7 @@ func (i *Identity) PublicKey() ed25519.PublicKey {
 	return *i.edpubk
 }
 
-// EDH performs a diffie-helman operation on this identities private key with the given public key.
+// EDH performs a diffie-hellman operation on this identities private key with the given public key.
 func (i *Identity) EDH(key ed25519.PublicKey) []byte {
 	secret := utils.EDH(*i.edpk, key)
 	return secret[:]
@@ -51,3 +51,8 @@ func (i *Identity) EDH(key ed25519.PublicKey) []byte {
 func (i *Identity) Hostname() string {
 	return utils.GetTorV3Hostname(*i.edpubk)
 }
+
+// Sign produces a signature for a given message attributable to the given identity
+func (i *Identity) Sign(input []byte) []byte {
+	return ed25519.Sign(*i.edpk, input)
+}

primitives/identity_test.go

@@ -0,0 +1,17 @@
+package primitives
+
+import (
+	"testing"
+)
+
+func TestIdentity_EDH(t *testing.T) {
+
+	id1, _ := InitializeEphemeralIdentity()
+	id2, _ := InitializeEphemeralIdentity()
+
+	k1 := id1.EDH(id2.PublicKey())
+	k2 := id2.EDH(id1.PublicKey())
+
+	t.Logf("k1: %x\nk2: %x\n", k1, k2)
+
+}

primitives/privacypass/common.go

@@ -0,0 +1,17 @@
+package privacypass
+
+// Transcript Constants
+const (
+	BatchProofProtocol = "privacy-pass-batch-proof"
+	BatchProofX        = "X-batch"
+	BatchProofY        = "Y-batch"
+	BatchProofPVector  = "P-vector"
+	BatchProofQVector  = "Q-vector"
+
+	DLEQX = "X"
+	DLEQY = "Y"
+	DLEQP = "P"
+	DLEQQ = "Q"
+	DLEQA = "A"
+	DLEQB = "B"
+)

primitives/privacypass/dlogeq.go

@@ -0,0 +1,73 @@
+package privacypass
+
+import (
+	"crypto/rand"
+	"cwtch.im/tapir/primitives/core"
+	ristretto "github.com/gtank/ristretto255"
+)
+
+// DLEQProof encapsulates a Chaum-Pedersen DLEQ Proof
+//gut In Ernest F. Brickell, editor,CRYPTO’92,volume 740 ofLNCS, pages 89–105. Springer, Heidelberg,August 1993
+type DLEQProof struct {
+	C *ristretto.Scalar
+	S *ristretto.Scalar
+}
+
+// DiscreteLogEquivalenceProof constructs a valid DLEQProof for the given parameters and transcript
+// Given  Y = kX & Q = kP
+// Peggy: t := choose randomly from Zq
+//        A := tX
+//        B := tP
+//        c := H(transcript(X,Y,P,Q,A,B))
+//        s := (t + ck) mod q
+//
+// Sends c,s to Vicky
+func DiscreteLogEquivalenceProof(k *ristretto.Scalar, X *ristretto.Element, Y *ristretto.Element, P *ristretto.Element, Q *ristretto.Element, transcript *core.Transcript) DLEQProof {
+	private := make([]byte, 64)
+	rand.Read(private)
+	t := new(ristretto.Scalar)
+	t.FromUniformBytes(private)
+	A := new(ristretto.Element).ScalarMult(t, X)
+	B := new(ristretto.Element).ScalarMult(t, P)
+
+	transcript.AddToTranscript(DLEQX, X.Encode(nil))
+	transcript.AddToTranscript(DLEQY, Y.Encode(nil))
+	transcript.AddToTranscript(DLEQP, P.Encode(nil))
+	transcript.AddToTranscript(DLEQQ, Q.Encode(nil))
+	transcript.AddToTranscript(DLEQA, A.Encode(nil))
+	transcript.AddToTranscript(DLEQB, B.Encode(nil))
+
+	c := transcript.CommitToTranscriptScalar("c")
+	s := new(ristretto.Scalar).Subtract(t, new(ristretto.Scalar).Multiply(c, k))
+	return DLEQProof{c, s}
+}
+
+// VerifyDiscreteLogEquivalenceProof verifies the DLEQ for the given parameters and transcript
+// Given  Y = kX & Q = kP  and Proof = (c,s)
+// Vicky: X' := sX
+//        Y' := cY
+//        P' := sP
+//        Q' := cQ
+//        A' = X'+Y' == sX + cY ?= sG + ckG == (s+ck)X == tX == A
+//        B' = P'+Q' == sP + cQ ?= sP + ckP == (s+ck)P == tP == B
+//        c' := H(transcript(X,Y,P,Q,A',B'))
+// Tests c ?= c
+func VerifyDiscreteLogEquivalenceProof(dleq DLEQProof, X *ristretto.Element, Y *ristretto.Element, P *ristretto.Element, Q *ristretto.Element, transcript *core.Transcript) bool {
+
+	Xs := new(ristretto.Element).ScalarMult(dleq.S, X)
+	Yc := new(ristretto.Element).ScalarMult(dleq.C, Y)
+	Ps := new(ristretto.Element).ScalarMult(dleq.S, P)
+	Qc := new(ristretto.Element).ScalarMult(dleq.C, Q)
+
+	A := new(ristretto.Element).Add(Xs, Yc)
+	B := new(ristretto.Element).Add(Ps, Qc)
+
+	transcript.AddToTranscript(DLEQX, X.Encode(nil))
+	transcript.AddToTranscript(DLEQY, Y.Encode(nil))
+	transcript.AddToTranscript(DLEQP, P.Encode(nil))
+	transcript.AddToTranscript(DLEQQ, Q.Encode(nil))
+	transcript.AddToTranscript(DLEQA, A.Encode(nil))
+	transcript.AddToTranscript(DLEQB, B.Encode(nil))
+
+	return transcript.CommitToTranscriptScalar("c").Equal(dleq.C) == 1
+}

primitives/privacypass/token.go

@@ -0,0 +1,117 @@
+package privacypass
+
+import (
+	"crypto/hmac"
+	"crypto/rand"
+	"cwtch.im/tapir/primitives/core"
+	"fmt"
+	"git.openprivacy.ca/openprivacy/libricochet-go/log"
+	ristretto "github.com/gtank/ristretto255"
+
+	"golang.org/x/crypto/sha3"
+)
+
+// Token is an implementation of PrivacyPass
+// Davidson A, Goldberg I, Sullivan N, Tankersley G, Valsorda F. Privacy pass: Bypassing internet challenges anonymously. Proceedings on Privacy Enhancing Technologies. 2018 Jun 1;2018(3):164-80.
+type Token struct {
+	t []byte
+	r *ristretto.Scalar
+	W *ristretto.Element
+}
+
+// GetT returns the underlying bytes for token for use in constraint proofs.
+func (t Token) GetT() []byte {
+	return t.t
+}
+
+// BlindedToken encapsulates a Blinded Token
+type BlindedToken struct {
+	P *ristretto.Element
+}
+
+// SignedToken encapsulates a Signed (Blinded) Token
+type SignedToken struct {
+	Q *ristretto.Element
+}
+
+// SpentToken encapsulates the parameters needed to spend a Token
+type SpentToken struct {
+	T   []byte
+	MAC []byte
+}
+
+// TokenPaymentHandler defines an interface with external payment processors
+type TokenPaymentHandler interface {
+	MakePayment()
+	// Next Token
+	NextToken(data []byte, hostname string) (SpentToken, error)
+}
+
+// GenBlindedToken initializes the Token
+// GenToken() & Blind()
+func (t *Token) GenBlindedToken() BlindedToken {
+	t.t = make([]byte, 32)
+	rand.Read(t.t)
+	t.r = new(ristretto.Scalar)
+	b := make([]byte, 64)
+	rand.Read(b)
+	t.r.FromUniformBytes(b)
+
+	Ht := sha3.Sum512(t.t)
+	T := new(ristretto.Element).FromUniformBytes(Ht[:])
+	P := new(ristretto.Element).ScalarMult(t.r, T)
+	return BlindedToken{P}
+}
+
+// unblindSignedToken unblinds a token that has been signed by a server
+func (t *Token) unblindSignedToken(token SignedToken) {
+	t.W = new(ristretto.Element).ScalarMult(new(ristretto.Scalar).Invert(t.r), token.Q)
+}
+
+// SpendToken binds the token with data and then redeems the token
+func (t *Token) SpendToken(data []byte) SpentToken {
+	key := sha3.Sum256(append(t.t, t.W.Encode(nil)...))
+	mac := hmac.New(sha3.New512, key[:])
+	return SpentToken{t.t, mac.Sum(data)}
+}
+
+// GenerateBlindedTokenBatch generates a batch of blinded tokens (and their unblinded equivalents)
+func GenerateBlindedTokenBatch(num int) (tokens []*Token, blindedTokens []BlindedToken) {
+	for i := 0; i < num; i++ {
+		tokens = append(tokens, new(Token))
+		blindedTokens = append(blindedTokens, tokens[i].GenBlindedToken())
+	}
+	return
+}
+
+// verifyBatchProof verifies a given batch proof (see also UnblindSignedTokenBatch)
+func verifyBatchProof(dleq DLEQProof, Y *ristretto.Element, blindedTokens []BlindedToken, signedTokens []SignedToken, transcript *core.Transcript) bool {
+	transcript.NewProtocol(BatchProofProtocol)
+	transcript.AddToTranscript(BatchProofX, new(ristretto.Element).Base().Encode(nil))
+	transcript.AddToTranscript(BatchProofY, Y.Encode(nil))
+	transcript.AddToTranscript(BatchProofPVector, []byte(fmt.Sprintf("%v", blindedTokens)))
+	transcript.AddToTranscript(BatchProofQVector, []byte(fmt.Sprintf("%v", signedTokens)))
+	prng := transcript.CommitToPRNG("w")
+	M := new(ristretto.Element).Zero()
+	Z := new(ristretto.Element).Zero()
+	for i := range blindedTokens {
+		c := prng.Next()
+		M = new(ristretto.Element).Add(new(ristretto.Element).ScalarMult(c, blindedTokens[i].P), M)
+		Z = new(ristretto.Element).Add(new(ristretto.Element).ScalarMult(c, signedTokens[i].Q), Z)
+	}
+	return VerifyDiscreteLogEquivalenceProof(dleq, new(ristretto.Element).Base(), Y, M, Z, transcript)
+}
+
+// UnblindSignedTokenBatch taking in a set of tokens, their blinded & signed counterparts, a server public key (Y), a DLEQ proof and a transcript
+// verifies that the signing procedure has taken place correctly and unblinds the tokens.
+func UnblindSignedTokenBatch(tokens []*Token, blindedTokens []BlindedToken, signedTokens []SignedToken, Y *ristretto.Element, proof DLEQProof, transcript *core.Transcript) bool {
+	verified := verifyBatchProof(proof, Y, blindedTokens, signedTokens, transcript)
+	if !verified {
+		log.Debugf("Failed to unblind tokens: %v", transcript.OutputTranscriptToAudit())
+		return false
+	}
+	for i, t := range tokens {
+		t.unblindSignedToken(signedTokens[i])
+	}
+	return true
+}

primitives/privacypass/token_test.go

@@ -0,0 +1,101 @@
+package privacypass
+
+import (
+	"cwtch.im/tapir/persistence"
+	"cwtch.im/tapir/primitives/core"
+	"git.openprivacy.ca/openprivacy/libricochet-go/log"
+	"github.com/gtank/ristretto255"
+	"golang.org/x/crypto/sha3"
+	"testing"
+)
+
+func TestToken_SpendToken(t *testing.T) {
+	server := NewTokenServer()
+
+	token := new(Token)
+	blindedToken := token.GenBlindedToken()
+
+	signedToken := server.SignBlindedToken(blindedToken)
+	token.unblindSignedToken(signedToken)
+
+	spentToken := token.SpendToken([]byte("Hello"))
+
+	if server.SpendToken(spentToken, []byte("Hello World")) == nil {
+		t.Errorf("Token Should be InValid")
+	}
+
+	if err := server.SpendToken(spentToken, []byte("Hello")); err != nil {
+		t.Errorf("Token Should be Valid: %v", err)
+	}
+
+	if err := server.SpendToken(spentToken, []byte("Hello")); err == nil {
+		t.Errorf("Token Should be Spent")
+	}
+}
+
+func TestToken_ConstrainToToken(t *testing.T) {
+	server := NewTokenServer()
+
+	token := new(Token)
+	blindedToken := token.GenBlindedToken()
+
+	signedToken := server.SignBlindedToken(blindedToken)
+	token.unblindSignedToken(signedToken)
+
+	spentToken := token.SpendToken([]byte("Hello"))
+
+	if server.SpendToken(spentToken, []byte("Hello World")) == nil {
+		t.Errorf("Token Should be InValid")
+	}
+
+	token2 := new(Token)
+	blindedToken2 := token2.GenBlindedToken()
+	Ht := sha3.Sum512(token.t)
+	T := new(ristretto255.Element).FromUniformBytes(Ht[:])
+	// Constraint forces T = kW to be part of the batch proof
+	// And because the batch proof must prove that *all* inputs share the same key and also checks the servers public key
+	// We get a consistency check for almost free.
+	signedTokens := server.SignBlindedTokenBatchWithConstraint([]BlindedToken{blindedToken2}, token.t, core.NewTranscript(""))
+	transcript := core.NewTranscript("")
+
+	// NOTE: For this to work token.t and token.W need to be obtain by the client from known source e.g. a public message board.
+	t.Logf("Result of constaint proof %v", UnblindSignedTokenBatch([]*Token{token2}, []BlindedToken{blindedToken2, {P: T}}, append(signedTokens.SignedTokens, SignedToken{token.W}), server.Y, signedTokens.Proof, transcript))
+	t.Log(transcript.OutputTranscriptToAudit())
+}
+
+func TestGenerateBlindedTokenBatch(t *testing.T) {
+	log.SetLevel(log.LevelDebug)
+	db := new(persistence.BoltPersistence)
+	db.Open("tokens.db")
+	defer db.Close()
+	server := NewTokenServerFromStore(db)
+
+	clientTranscript := core.NewTranscript("privacyPass")
+	serverTranscript := core.NewTranscript("privacyPass")
+
+	tokens, blindedTokens := GenerateBlindedTokenBatch(10)
+	batchProof := server.SignBlindedTokenBatch(blindedTokens, serverTranscript)
+
+	verified := UnblindSignedTokenBatch(tokens, blindedTokens, batchProof.SignedTokens, server.Y, batchProof.Proof, clientTranscript)
+
+	if !verified {
+		t.Errorf("Something went wrong, the proof did not pass")
+	}
+
+	// Attempt to Spend All the tokens
+	for _, token := range tokens {
+		spentToken := token.SpendToken([]byte("Hello"))
+		if err := server.SpendToken(spentToken, []byte("Hello")); err != nil {
+			t.Errorf("Token Should be Valid: %v", err)
+		}
+	}
+
+	t.Logf("Client Transcript,: %s", clientTranscript.OutputTranscriptToAudit())
+	t.Logf("Server Transcript,: %s", serverTranscript.OutputTranscriptToAudit())
+
+	wrongTranscript := core.NewTranscript("wrongTranscript")
+	verified = UnblindSignedTokenBatch(tokens, blindedTokens, batchProof.SignedTokens, server.Y, batchProof.Proof, wrongTranscript)
+	if verified {
+		t.Errorf("Something went wrong, the proof passed with wrong transcript: %s", wrongTranscript.OutputTranscriptToAudit())
+	}
+}

primitives/privacypass/tokenserver.go

@@ -0,0 +1,150 @@
+package privacypass
+
+import (
+	"crypto/hmac"
+	"crypto/rand"
+	"cwtch.im/tapir/persistence"
+	"cwtch.im/tapir/primitives/core"
+	"encoding/hex"
+	"fmt"
+	ristretto "github.com/gtank/ristretto255"
+	"golang.org/x/crypto/sha3"
+	"sync"
+)
+
+// TokenServer implements a token server.
+type TokenServer struct {
+	k                  *ristretto.Scalar
+	Y                  *ristretto.Element
+	seen               map[string]bool
+	persistanceService persistence.Service
+	mutex              sync.Mutex
+}
+
+// SignedBatchWithProof encapsulates a signed batch of blinded tokens with a batch proof for verification
+type SignedBatchWithProof struct {
+	SignedTokens []SignedToken `json:"st"`
+	Proof        DLEQProof     `json:"dp"`
+}
+
+const tokenBucket = "tokens"
+const keyBucket = "keys"
+
+// NewTokenServer generates a new TokenServer (used mostly for testing with ephemeral instances)
+func NewTokenServer() *TokenServer {
+	k := new(ristretto.Scalar)
+	b := make([]byte, 64)
+	_, err := rand.Read(b)
+	if err != nil {
+		// unable to generate secure random numbers
+		panic("unable to generate secure random numbers")
+	}
+	k.FromUniformBytes(b)
+	return &TokenServer{k, new(ristretto.Element).ScalarBaseMult(k), make(map[string]bool), nil, sync.Mutex{}}
+}
+
+// NewTokenServerFromStore generates a new TokenServer backed by a persistence service.
+func NewTokenServerFromStore(persistenceService persistence.Service) *TokenServer {
+	tokenServer := NewTokenServer()
+	persistenceService.Setup([]string{tokenBucket})
+	persistenceService.Setup([]string{keyBucket})
+	exists, err := persistenceService.Check(keyBucket, "k")
+	if err != nil {
+		panic(err)
+	}
+	// if we don't have a stored k then save the one we have generated
+	// otherwise use the k we have stored
+	if !exists {
+		persistenceService.Persist(keyBucket, "k", tokenServer.k)
+	} else {
+		persistenceService.Load(keyBucket, "k", tokenServer.k)
+
+		// recalculate public key from stored k
+		tokenServer.Y = new(ristretto.Element).ScalarBaseMult(tokenServer.k)
+	}
+
+	tokenServer.persistanceService = persistenceService
+	return tokenServer
+}
+
+// SignBlindedToken calculates kP for the given BlindedToken P
+func (ts *TokenServer) SignBlindedToken(bt BlindedToken) SignedToken {
+	Q := new(ristretto.Element).ScalarMult(ts.k, bt.P)
+	return SignedToken{Q}
+}
+
+// SignBlindedTokenBatch signs a batch of blinded tokens under a given transcript
+func (ts *TokenServer) SignBlindedTokenBatch(blindedTokens []BlindedToken, transcript *core.Transcript) SignedBatchWithProof {
+	var signedTokens []SignedToken
+	for _, bt := range blindedTokens {
+		signedTokens = append(signedTokens, ts.SignBlindedToken(bt))
+	}
+	return SignedBatchWithProof{signedTokens, ts.constructBatchProof(blindedTokens, signedTokens, transcript)}
+}
+
+// SignBlindedTokenBatchWithConstraint signs a batch of blinded tokens under a given transcript given a constraint that the tokens must be signed
+// by the same public key as an existing token
+func (ts *TokenServer) SignBlindedTokenBatchWithConstraint(blindedTokens []BlindedToken, constraintToken []byte, transcript *core.Transcript) SignedBatchWithProof {
+	var signedTokens []SignedToken
+	for _, bt := range blindedTokens {
+		signedTokens = append(signedTokens, ts.SignBlindedToken(bt))
+	}
+	Ht := sha3.Sum512(constraintToken)
+	T := new(ristretto.Element).FromUniformBytes(Ht[:])
+	// W == kT
+	W := new(ristretto.Element).ScalarMult(ts.k, T)
+	blindedTokens = append(blindedTokens, BlindedToken{P: T})
+	return SignedBatchWithProof{signedTokens, ts.constructBatchProof(blindedTokens, append(signedTokens, SignedToken{Q: W}), transcript)}
+}
+
+// constructBatchProof construct a batch proof that all the signed tokens have been signed correctly
+func (ts *TokenServer) constructBatchProof(blindedTokens []BlindedToken, signedTokens []SignedToken, transcript *core.Transcript) DLEQProof {
+	transcript.NewProtocol(BatchProofProtocol)
+	transcript.AddToTranscript(BatchProofX, new(ristretto.Element).Base().Encode(nil))
+	transcript.AddToTranscript(BatchProofY, ts.Y.Encode(nil))
+	transcript.AddToTranscript(BatchProofPVector, []byte(fmt.Sprintf("%v", blindedTokens)))
+	transcript.AddToTranscript(BatchProofQVector, []byte(fmt.Sprintf("%v", signedTokens)))
+	prng := transcript.CommitToPRNG("w")
+
+	M := new(ristretto.Element).Zero()
+	Z := new(ristretto.Element).Zero()
+
+	for i := range blindedTokens {
+		c := prng.Next()
+		M = new(ristretto.Element).Add(new(ristretto.Element).ScalarMult(c, blindedTokens[i].P), M)
+		Z = new(ristretto.Element).Add(new(ristretto.Element).ScalarMult(c, signedTokens[i].Q), Z)
+	}
+	return DiscreteLogEquivalenceProof(ts.k, new(ristretto.Element).Base(), ts.Y, M, Z, transcript)
+}
+
+// SpendToken returns true a SpentToken is valid and has never been spent before, false otherwise.
+func (ts *TokenServer) SpendToken(token SpentToken, data []byte) error {
+	ts.mutex.Lock()
+	defer ts.mutex.Unlock() // We only want 1 client at a time redeeming tokens to prevent double-spends
+	if ts.persistanceService == nil {
+		if _, spent := ts.seen[hex.EncodeToString(token.T)]; spent {
+			return fmt.Errorf("token: %v has already been spent", token)
+		}
+	} else {
+		spent, err := ts.persistanceService.Check(tokenBucket, hex.EncodeToString(token.T))
+		if err != nil || spent == true {
+			return fmt.Errorf("token: %v has already been spent", token)
+		}
+	}
+	Ht := sha3.Sum512(token.T)
+	T := new(ristretto.Element).FromUniformBytes(Ht[:])
+	W := new(ristretto.Element).ScalarMult(ts.k, T)
+	key := sha3.Sum256(append(token.T, W.Encode(nil)...))
+	mac := hmac.New(sha3.New512, key[:])
+	computedMAC := mac.Sum(data)
+	result := hmac.Equal(token.MAC, computedMAC)
+	if result == true {
+		if ts.persistanceService == nil {
+			ts.seen[hex.EncodeToString(token.T)] = true
+		} else {
+			ts.persistanceService.Persist(tokenBucket, hex.EncodeToString(token.T), true)
+		}
+		return nil
+	}
+	return fmt.Errorf("token: %v is invalid and/or has not been signed by this service", token)
+}

primitives/time.go

@@ -1,21 +0,0 @@
-package primitives
-
-import (
-	"time"
-)
-
-// TimeProvider is an interface used by services to timestamp events. Why not just have them use time.Now()? We want
-// to be able to write tests that simulate behavior over several hours, and thus having an interface to abstract away
-// time details for the services is very useful.
-type TimeProvider interface {
-	GetCurrentTime() time.Time
-}
-
-// OSTimeProvider provides a wrapper around time provider which simply provides the time as given by the operating system.
-type OSTimeProvider struct {
-}
-
-// GetCurrentTime returns the time provided by the OS
-func (ostp OSTimeProvider) GetCurrentTime() time.Time {
-	return time.Now()
-}

primitives/transcript.go

@@ -1,51 +0,0 @@
-package primitives
-
-import (
-	"fmt"
-	"golang.org/x/crypto/sha3"
-	"hash"
-)
-
-// Transcript implements a transcript of a public coin argument.
-//
-// We have the following goals:
-//  - Provide a consisted transcript API for our zero knowledge protocols
-//  - Allow sequential proofs over a common transcript (ensuring a single proof cannot be extracted standalone)
-//  - produce an auditable human-readable transcript.
-//
-// The design of this API was inspired by Merlin: https://docs.rs/crate/merlin/
-//
-// At some point we might want to extend this to be compatible with Merlin transcripts, built on STROBE
-type Transcript struct {
-	hash       hash.Hash
-	transcript string
-}
-
-// NewTranscript creates a new Transcript with the given Label, the label should be unique to the application
-func NewTranscript(label string) *Transcript {
-	transcript := new(Transcript)
-	transcript.hash = sha3.New256()
-	transcript.AddToTranscript("protocol", []byte(label))
-	return transcript
-}
-
-// AddToTranscript appends a value to the transcript with the given label
-// This binds the given data to the label.
-func (t *Transcript) AddToTranscript(label string, b []byte) {
-	op := fmt.Sprintf("%s (%d) %x;", label, len(b), b)
-	t.transcript = fmt.Sprintf("%v\n%v", t.transcript, op)
-	t.hash.Write([]byte(op))
-}
-
-// OutputTranscriptToAudit outputs a human-readable copy of the transcript so far.
-func (t Transcript) OutputTranscriptToAudit() string {
-	return t.transcript
-}
-
-// CommitToTranscript generates a challenge based on the current transcript, it also commits the challenge to the transcript.
-func (t *Transcript) CommitToTranscript(label string) []byte {
-	t.AddToTranscript("commit", []byte(label))
-	b := t.hash.Sum([]byte{})
-	t.AddToTranscript(label, b)
-	return b
-}

service.go

@@ -9,7 +9,6 @@ import (
 	"golang.org/x/crypto/ed25519"
 	"golang.org/x/crypto/nacl/secretbox"
 	"io"
-	"net"
 	"sync"
 )
 
@@ -19,7 +18,7 @@ type Service interface {
 	Connect(hostname string, application Application) (bool, error)
 	Listen(application Application) error
 	GetConnection(connectionID string) (Connection, error)
-	WaitForCapabilityOrClose(connectionID string, capability string) (Connection, error)
+	WaitForCapabilityOrClose(connectionID string, capability Capability) (Connection, error)
 	Shutdown()
 }
 
@@ -30,19 +29,20 @@ type Connection interface {
 	ID() *primitives.Identity
 	Expect() []byte
 	SetHostname(hostname string)
-	HasCapability(name string) bool
-	SetCapability(name string)
+	HasCapability(name Capability) bool
+	SetCapability(name Capability)
 	SetEncryptionKey(key [32]byte)
 	Send(message []byte)
 	Close()
 	App() Application
+	SetApp(application Application)
 	IsClosed() bool
 }
 
 // Connection defines a Tapir Connection
 type connection struct {
 	hostname     string