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StrobeGo does not support continuation ops 

Because Strobe encodes the operation, doing two meta-AD operations is
different from doing one meta-AD operation with the concatenated data.
Other Strobe implementations, such as the one internal to the Merlin
implementation in Rust, support a "continuation" flag that indicates
that some data is a continuation of a previous operation, rather than a
new one.  However, StrobeGo does not, so the previous code was doing two
separate operations.  This code may do more allocations than necessary,
as I have never understood the semantics of Go slices.
This commit is contained in:
Henry de Valence 2019-10-07 22:58:38 -07:00 committed by George Tankersley
parent 8dedea481f
commit e9014b45c3
1 changed files with 10 additions and 4 deletions
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14
merlin.go
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@ -36,8 +36,11 @@ func (t *Transcript) AppendMessage(label, message []byte) {
fmt.Printf("meta-AD : %x || LE32(%d)\t# b\"%s\"\n", label, len(message), label)
t.s.AD(true, label)
t.s.AD(true, sizeBuffer)
// The StrobeGo API does not support continuation operations,
// so we have to pass the label and length as a single buffer.
// Otherwise it will record two meta-AD operations instead of one.
labelSize := append(label, sizeBuffer...)
t.s.AD(true, labelSize)
fmt.Printf("AD : %x\t# b\"%s\"\n", message, message)
t.s.AD(false, message)
@ -53,8 +56,11 @@ func (t *Transcript) ExtractBytes(label []byte, outLen int) []byte {
fmt.Printf("meta-AD : %x || LE32(%d)\t# b\"%s\"\n", label, outLen, label)
t.s.AD(true, label)
t.s.AD(true, sizeBuffer)
// The StrobeGo API does not support continuation operations,
// so we have to pass the label and length as a single buffer.
// Otherwise it will record two meta-AD operations instead of one.
labelSize := append(label, sizeBuffer...)
t.s.AD(true, labelSize)
// a PRF call directly to the output buffer would be better
return t.s.PRF(outLen)