Adding a PoW Token Service that Grants Tokens for PoW

.gitignore

@@ -3,3 +3,5 @@ vendor/
 /tor/
 coverage.out
 /testing/tor/
+/applications/tor/
+*.db

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()}
@@ -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")

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().Bytes()
+
+		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 +1,56 @@
+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")
+
+// NewInstance should always return a new instantiation of the application.
+func (powapp *TokenApplication) NewInstance() tapir.Application {
+	app := new(TokenApplication)
+	app.TokenService = powapp.TokenService
+	return app
+}
+
+// Init is run when the connection is first started.
+func (powapp *TokenApplication) Init(connection tapir.Connection) {
+	powapp.Transcript().NewProtocol("token-app")
+	if connection.IsOutbound() {
+		tokens, blinded := privacypass.GenerateBlindedTokenBatch(10)
+		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, powapp.TokenService.Y, signedBatch.Proof, powapp.Transcript())
+			if verified {
+				log.Debugf("Successfully obtained signed tokens")
+				powapp.Tokens = tokens
+				connection.SetCapability(HasTokensCapability)
+				return
+			}
+			log.Debugf("Failed to verify signed token batch")
+		}
+	} else {
+		var blinded []privacypass.BlindedToken
+		err := json.Unmarshal(connection.Expect(), &blinded)
+		if err == nil {
+			batchProof := powapp.TokenService.SignBlindedTokenBatch(blinded, powapp.Transcript())
+			data, _ := json.Marshal(batchProof)
+			connection.Send(data)
+			return
+		}
+	}
+}

applications/tokenboard/client.go

@@ -0,0 +1,112 @@
+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)
+		log.Debugf("Received a Message: %v", 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)
+	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 +1,90 @@
+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"
+)
+
+// 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)
+		log.Debugf("Received a Message: %v", 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, message); 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 +1,149 @@
+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)
+	client.WaitForCapabilityOrClose(fph.ServerHostname, applications.HasTokensCapability)
+	conn, _ := client.GetConnection(fph.ServerHostname)
+	powtapp, _ := conn.App().(*applications.TokenApplication)
+	fph.tokens = append(fph.tokens, powtapp.Tokens...)
+	log.Debugf("Transcript: %v", powtapp.Transcript().OutputTranscriptToAudit())
+	conn.Close()
+}
+
+func (fph *FreePaymentHandler) NextToken(data []byte) (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(data), 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 * 30) // 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
+}

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 {

persistence/bolt_persistence.go

@@ -0,0 +1,76 @@
+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 +1,185 @@
+package auditable
+
+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

@@ -2,6 +2,8 @@ package primitives
 
 import (
 	"crypto/sha256"
+	"math"
+	"math/big"
 	"sync"
 )
 
@@ -12,32 +14,30 @@ type BloomFilter struct {
 }
 
 // Init constructs a bloom filter of size m
-func (bf *BloomFilter) Init(m int16) {
+func (bf *BloomFilter) Init(m int64) {
 	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))
+	// Not the fastest hash function ever, but cryptographic security is more important than speed.
+	hash1 := sha256.Sum256(append([]byte("h1"), msg...))
+	hash2 := sha256.Sum256(append([]byte("h2"), msg...))
+	hash3 := sha256.Sum256(append([]byte("h3"), msg...))
+	hash4 := sha256.Sum256(append([]byte("h4"), msg...))
 
-	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))
+	m := int64(len(bf.B))
+	// Number of bytes needed to pick a position from [0,m)
+	B := int(math.Ceil(math.Log2(float64(m)) / 8.0))
 
-	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))
+	p1 := big.NewInt(0).SetBytes(hash1[:B]).Int64()
+	p2 := big.NewInt(0).SetBytes(hash2[:B]).Int64()
+	p3 := big.NewInt(0).SetBytes(hash3[:B]).Int64()
+	p4 := big.NewInt(0).SetBytes(hash4[:B]).Int64()
 
-	return []int{pos1, pos2, pos3, pos4}
+	return []int{int(p1), int(p2), int(p3), int(p4)}
 }
 
 // Insert updates the BloomFilter (suitable for concurrent use)

primitives/bloom_test.go

@@ -0,0 +1,24 @@
+package primitives
+
+import (
+	"strconv"
+	"testing"
+)
+
+func TestBloomFilter_Insert(t *testing.T) {
+	bf := new(BloomFilter)
+	bf.Init(256)
+
+	fp := 0
+	for i := 0; i < 256; i++ {
+		input := []byte("test" + strconv.Itoa(256+i))
+		if bf.Check(input) {
+			t.Log("False Positive!")
+			fp++
+		}
+		bf.Insert(input)
+	}
+
+	t.Logf("Num false positives %v %v%%", fp, (float64(fp)/256.0)*100)
+
+}

primitives/transcript.go → primitives/core/transcript.go

@@ -1,9 +1,11 @@
-package primitives
+package core
 
 import (
 	"fmt"
+	"github.com/bwesterb/go-ristretto"
 	"golang.org/x/crypto/sha3"
 	"hash"
+	"io"
 )
 
 // Transcript implements a transcript of a public coin argument.
@@ -42,6 +44,14 @@ 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.hash.Write([]byte(op))
+}
+
 // 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))
@@ -49,3 +59,33 @@ func (t *Transcript) CommitToTranscript(label string) []byte {
 	t.AddToTranscript(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 := [32]byte{}
+	io.ReadFull(prng.prng, buf[:])
+	return new(ristretto.Scalar).SetBytes(&buf)
+}
+
+// CommitToPRNG commits the label to the transcript and derives a PRNG from the transcript.
+func (t *Transcript) CommitToPRNG(label string) PRNG {
+	t.AddToTranscript("commit-prng", []byte(label))
+	b := t.hash.Sum([]byte{})
+	t.AddToTranscript(label, b)
+	prng := sha3.NewShake256()
+	prng.Write(b)
+	return PRNG{prng: prng}
+}
+
+// CommitToTranscriptScalar is a convenience method for CommitToTranscript which returns a ristretto Scalar
+func (t *Transcript) CommitToTranscriptScalar(label string) *ristretto.Scalar {
+	c := t.CommitToTranscript(label)
+	cs := [32]byte{}
+	copy(cs[:], c[:])
+	return new(ristretto.Scalar).SetBytes(&cs)
+}

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/dlog.go

@@ -0,0 +1,71 @@
+package primitives
+
+import (
+	"cwtch.im/tapir/primitives/core"
+	"github.com/bwesterb/go-ristretto"
+)
+
+// DLProof Encapsulates a Discrete Log / Schnorr Proof
+// Note that these parameters are read-only.
+type DLProof struct {
+	V, A ristretto.Point
+	R    ristretto.Scalar
+}
+
+// DiscreteLogProof - Proof of Knowledge of Exponent
+// Given  V = xG
+// Peggy: z := choose randomly from Zq
+//        A := zG
+//        c := H(transcript(G,V,A)) mod q
+//        r := (z + cx) mod q
+//
+// Sends A,r,V to Vicky
+func DiscreteLogProof(x ristretto.Scalar, v ristretto.Point, transcript *core.Transcript) (proof DLProof) {
+
+	transcript.AddToTranscript("G", new(ristretto.Point).SetBase().Bytes())
+
+	// We bind the proof to our public V
+	proof.V = v
+	transcript.AddToTranscript("V", proof.V.Bytes())
+
+	// Generate a random z
+	// A := zG
+	z := new(ristretto.Scalar).Rand()
+	proof.A = *new(ristretto.Point).ScalarMultBase(z)
+	transcript.AddToTranscript("A", proof.A.Bytes())
+
+	// Derive Challenge
+	c := transcript.CommitToTranscriptScalar("c")
+
+	// r := (z + cx) mod p
+	cx := new(ristretto.Scalar).Mul(c, &x)
+	proof.R = *new(ristretto.Scalar).Add(z, cx)
+
+	return
+}
+
+// VerifyDiscreteLogProof validates a given Schnorr Proof
+// Vicky gets A,r,V from Peggy
+// Vicky computes c := H(transcript(G,V,A)) mod q
+// Vicky checks rG := A + cV
+//              rG ?= zG + cV
+//         (z+cx)G ?= zG + cV
+//                 ?= zG + cxG
+// Thus demonstrating that Peggy knows the discrete log to V
+func VerifyDiscreteLogProof(proof DLProof, transcript *core.Transcript) bool {
+
+	transcript.AddToTranscript("G", new(ristretto.Point).SetBase().Bytes())
+	transcript.AddToTranscript("V", proof.V.Bytes())
+	transcript.AddToTranscript("A", proof.A.Bytes())
+	c := transcript.CommitToTranscriptScalar("c")
+
+	// Compute left hand side
+	lhs := new(ristretto.Point).ScalarMultBase(&proof.R)
+
+	// Compute right hand side
+	cV := new(ristretto.Point).ScalarMult(&proof.V, c)
+	rhs := new(ristretto.Point).Add(&proof.A, cV)
+
+	// Result of verification: lhs ?= rhs
+	return lhs.Equals(rhs)
+}

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 +1,69 @@
+package privacypass
+
+import (
+	"cwtch.im/tapir/primitives/core"
+	"github.com/bwesterb/go-ristretto"
+)
+
+// DLEQProof encapsulates a Chaum-Pedersen DLEQ Proof
+// David Chaum and Torben P. Pedersen. Wallet databaseswith observers. 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  P = kX, Q = kP, Y=kX
+// 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.Point, Y *ristretto.Point, P *ristretto.Point, Q *ristretto.Point, transcript *core.Transcript) DLEQProof {
+	t := new(ristretto.Scalar).Rand()
+	A := new(ristretto.Point).ScalarMult(X, t)
+	B := new(ristretto.Point).ScalarMult(P, t)
+
+	transcript.AddToTranscript(DLEQX, X.Bytes())
+	transcript.AddToTranscript(DLEQY, Y.Bytes())
+	transcript.AddToTranscript(DLEQP, P.Bytes())
+	transcript.AddToTranscript(DLEQQ, Q.Bytes())
+	transcript.AddToTranscript(DLEQA, A.Bytes())
+	transcript.AddToTranscript(DLEQB, B.Bytes())
+
+	c := transcript.CommitToTranscriptScalar("c")