Answers for "bm"

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-Clause

bm

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;
    }