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rfc6979: Add leading zeros if r or s has less than 32 bytes

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SignECDSA function returns two coordinates on elliptic curve.
Catenation of these coordinates is a 64 byte signature. If
one of these coordinates have less than 32 significant bytes, then
it should have leading zeros.
This commit is contained in:
alexvanin 2020-03-01 16:50:38 +03:00
parent 5ba9a8ffc6
commit 1461d7a248
1 changed files with 12 additions and 1 deletions
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13
rfc6979.go
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@ -38,7 +38,18 @@ func SignRFC6979(key *ecdsa.PrivateKey, msg []byte) ([]byte, error) {
return nil, ErrEmptyPrivateKey
}
r, s := rfc6979.SignECDSA(key, hashBytesRFC6979(msg), sha256.New)
return append(r.Bytes(), s.Bytes()...), nil
rBytes, sBytes := r.Bytes(), s.Bytes()
signature := make([]byte, RFC6979SignatureSize)
// if `r` has less than 32 bytes, add leading zeros
ind := RFC6979SignatureSize/2 - len(rBytes)
copy(signature[ind:], rBytes)
// if `s` has less than 32 bytes, add leading zeros
ind = RFC6979SignatureSize - len(sBytes)
copy(signature[ind:], sBytes)
return signature, nil
}
func decodeSignature(sig []byte) (*big.Int, *big.Int, error) {