bm
BIP: 137
Layer: Applications
Title: Signatures of Messages using Private Keys
Author: Christopher Gilliard <[email protected]>
Comments-Summary: No comments yet.
Comments-URI: https://github.com/bitcoin/bips/wiki/Comments:BIP-0137
Status: Final
Type: Standards Track
Created: 2019-02-16
License: BSD-2-Clausebm
public static ECKey signedMessageToKey(String message, String signatureBase64) throws SignatureException {
byte[] signatureEncoded;
try {
signatureEncoded = Base64.decode(signatureBase64);
} catch (RuntimeException e) {
// This is what you get back from Bouncy Castle if base64 doesn't decode :(
throw new SignatureException("Could not decode base64", e);
}
// Parse the signature bytes into r/s and the selector value.
if (signatureEncoded.length < 65)
throw new SignatureException("Signature truncated, expected 65 bytes and got " + signatureEncoded.length);
int header = signatureEncoded[0] & 0xFF;
// The header byte: 0x1B = first key with even y, 0x1C = first key with odd y,
// 0x1D = second key with even y, 0x1E = second key with odd y
if (header < 27 || header > 42)
throw new SignatureException("Header byte out of range: " + header);
BigInteger r = new BigInteger(1, Arrays.copyOfRange(signatureEncoded, 1, 33));
BigInteger s = new BigInteger(1, Arrays.copyOfRange(signatureEncoded, 33, 65));
ECDSASignature sig = new ECDSASignature(r, s);
byte[] messageBytes = formatMessageForSigning(message);
// Note that the C++ code doesn't actually seem to specify any character encoding. Presumably it's whatever
// JSON-SPIRIT hands back. Assume UTF-8 for now.
Sha256Hash messageHash = Sha256Hash.twiceOf(messageBytes);
boolean compressed = false;
// this section is added to support new signature types
if(header>= 39) // this is a bech32 signature
{
header -= 12;
compressed = true;
} // this is a segwit p2sh signature
else if(header >= 35)
{
header -= 8;
compressed = true;
} // this is a compressed key signature
else if (header >= 31) {
compressed = true;
header -= 4;
}
int recId = header - 27;
ECKey key = ECKey.recoverFromSignature(recId, sig, messageHash, compressed);
if (key == null)
throw new SignatureException("Could not recover public key from signature");
return key;
}Copyright © 2021 Codeinu
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