Method sign

security/src/main/java/pro/tools/security/sm/SM2.java:491–512

签名 @param M 签名信息 @param IDA 签名方唯一标识 @param keyPair 签名方密钥对 @return 签名

(String M, String IDA, SM2KeyPair keyPair)

     * @return 签名
     */
    public Signature sign(String M, String IDA, SM2KeyPair keyPair) {
        byte[] ZA = ZA(IDA, keyPair.getPublicKey());
        byte[] M_ = join(ZA, M.getBytes());
        BigInteger e = new BigInteger(1, sm3hash(M_));
        // BigInteger k = new BigInteger(
        // "6CB28D99 385C175C 94F94E93 4817663F C176D925 DD72B727 260DBAAE
        // 1FB2F96F".replace(" ", ""), 16);
        BigInteger k;
        BigInteger r;
        do {
            k = random(n);
            ECPoint p1 = G.multiply(k).normalize();
            BigInteger x1 = p1.getXCoord().toBigInteger();
            r = e.add(x1);
            r = r.mod(n);
        } while (r.equals(BigInteger.ZERO) || r.add(k).equals(n));

        BigInteger s = ((keyPair.getPrivateKey().add(BigInteger.ONE).modInverse(n))
                .multiply((k.subtract(r.multiply(keyPair.getPrivateKey()))).mod(n))).mod(n);

        return new Signature(r, s);
    }

    /**
     * 验签