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Modify the function of SignCanonical in btcec, do makeCompact after isCanonicalSig. #218

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Modify the function of SignCanonical in btcec, do makeCompact after isCanonicalSig. #218

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21 changes: 17 additions & 4 deletions btcsuite/btcd/btcec/privkey.go
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Original file line number Diff line number Diff line change
Expand Up @@ -65,21 +65,23 @@ func (p *PrivateKey) Sign(hash []byte) (*Signature, error) {

// SignCanonical goes through signatures and returns only a canonical
// representations. This matches the EOS blockchain expectations.
// do isCanonical before compactSig, for performance improvement
func (p *PrivateKey) SignCanonical(curve *KoblitzCurve, hash []byte) ([]byte, error) {
for i := 0; i < 25; i++ {
sig, err := signRFC6979(p, hash, i)
if err != nil {
return nil, err
}

compactSig, err := makeCompact(curve, sig, p, hash, true)
if err != nil {
if !isCanonicalSig(sig.R.Bytes(), sig.S.Bytes()) {
continue
}

if isCanonical(compactSig) {
return compactSig, nil
compactSig, err := makeCompact(curve, sig, p, hash, true)
if err != nil {
continue
}
return compactSig, nil
}
return nil, errors.New("couldn't find a canonical signature")
}
Expand Down Expand Up @@ -110,3 +112,14 @@ func isCanonical(compactSig []byte) bool {
t4 := !(d[33] == 0 && ((d[34] & 0x80) == 0))
return t1 && t2 && t3 && t4
}

// add function for original signature, do isCanonical before compactSig
func isCanonicalSig(r []byte, s []byte) bool {
rlen := len(r)
slen := len(s)
t1 := rlen < 32 || (r[0] & 0x80) == 0
t2 := !( (rlen < 32 || r[0] == 0) && ((rlen >= 31 && (r[rlen-31] & 0x80) == 0) || rlen < 31) )
t3 := slen < 32 || (s[0] & 0x80) == 0
t4 := !( (slen < 32 || s[0] == 0) && ((slen >= 31 && (s[slen-31] & 0x80) == 0) || slen < 31) )
return t1 && t2 && t3 && t4
}
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