C# .NET Framework 实现SM2加签、验签

本文只实现SM2的加签以及验签。
首先需要安装包 Portable.BouncyCastle。然后创建类 EasyGmutil

namespace ConsoleApp1
{
    public class EasyGmUtil
    {
        private static X9ECParameters x9ECParameters = GMNamedCurves.GetByName("sm2p256v1");
        private static ECDomainParameters ecDomainParameters = new ECDomainParameters(x9ECParameters.Curve, x9ECParameters.G, x9ECParameters.N);


        /**
          *
          * @param msg
          * @param userId
          * @param privateKey
          * @return r||s，直接拼接byte数组的rs
          */
        public static byte[] signSm3WithSm2(byte[] msg, byte[] userId, byte[] privateKeyBytes)
        {
            ECPrivateKeyParameters privateKeyParameters = getPrivatekeyFromD(new BigInteger(1, privateKeyBytes));
            return rsAsn1ToPlainByteArray(signSm3WithSm2Asn1Rs(msg, userId, privateKeyParameters));
        }


        /**
          * @param msg
          * @param userId
          * @param privateKey
          * @return rs in <b>asn1 format</b>
          */
        public static byte[] signSm3WithSm2Asn1Rs(byte[] msg, byte[] userId, AsymmetricKeyParameter privateKey)
        {
            try
            {
                ISigner signer = SignerUtilities.InitSigner("SM3withSM2", true, privateKey, new SecureRandom());
                signer.BlockUpdate(msg, 0, msg.Length);
                byte[] sig = signer.GenerateSignature();
                return sig;
            }
            catch (Exception e)
            {
                return null;
            }
        }


        /**
      *
      * @param msg
      * @param userId
      * @param rs r||s，直接拼接byte数组的rs
      * @param publicKey
      * @return
      */
        public static bool verifySm3WithSm2(byte[] msg, byte[] userId, byte[] rs, byte[] publicKeyBytes)
        {
            if (rs == null || msg == null || userId == null) return false;
            if (rs.Length != RS_LEN * 2) return false;

            if (publicKeyBytes.Length != 64 && publicKeyBytes.Length != 65) throw new ArgumentException("err key length");
            BigInteger x, y;
            if (publicKeyBytes.Length > 64)
            {
                x = fromUnsignedByteArray(publicKeyBytes, 1, 32);
                y = fromUnsignedByteArray(publicKeyBytes, 33, 32);
            }
            else
            {
                x = fromUnsignedByteArray(publicKeyBytes, 0, 32);
                y = fromUnsignedByteArray(publicKeyBytes, 32, 32);
            }
            ECPublicKeyParameters publicKey = getPublickeyFromXY(x, y);
            return verifySm3WithSm2Asn1Rs(msg, userId, rsPlainByteArrayToAsn1(rs), publicKey);
        }

        public static BigInteger fromUnsignedByteArray(byte[] var0, int var1, int var2)
        {
            byte[] var3 = var0;
            if (var1 != 0 || var2 != var0.Length)
            {
                var3 = new byte[var2];
                Array.Copy(var0, var1, var3, 0, var2);
            }

            return new BigInteger(1, var3);
        }

        /**
         *
         * @param msg
         * @param userId
         * @param rs in <b>asn1 format</b>
         * @param publicKey
         * @return
         */

        public static bool verifySm3WithSm2Asn1Rs(byte[] msg, byte[] userId, byte[] sign, AsymmetricKeyParameter publicKey)
        {
            try
            {
                ISigner signer = SignerUtilities.GetSigner("SM3withSM2");
                signer.Init(false, publicKey);
                signer.BlockUpdate(msg, 0, msg.Length);
                return signer.VerifySignature(sign);
            }
            catch (Exception e)
            {
                return false;
            }
        }

        public static ECPrivateKeyParameters getPrivatekeyFromD(BigInteger d)
        {
            return new ECPrivateKeyParameters(d, ecDomainParameters);
        }

        public static ECPublicKeyParameters getPublickeyFromXY(BigInteger x, BigInteger y)
        {
            return new ECPublicKeyParameters(x9ECParameters.Curve.CreatePoint(x, y), ecDomainParameters);
        }

        private const int RS_LEN = 32;

        private static byte[] bigIntToFixexLengthBytes(BigInteger rOrS)
        {
            // for sm2p256v1, n is 00fffffffeffffffffffffffffffffffff7203df6b21c6052b53bbf40939d54123,
            // r and s are the result of mod n, so they should be less than n and have length<=32
            byte[] rs = rOrS.ToByteArray();
            if (rs.Length == RS_LEN) return rs;
            else if (rs.Length == RS_LEN + 1 && rs[0] == 0) return Arrays.CopyOfRange(rs, 1, RS_LEN + 1);
            else if (rs.Length < RS_LEN)
            {
                byte[] result = new byte[RS_LEN];
                Arrays.Fill(result, (byte)0);
                Buffer.BlockCopy(rs, 0, result, RS_LEN - rs.Length, rs.Length);
                return result;
            }
            else
            {
                throw new ArgumentException("err rs: " + Hex.ToHexString(rs));
            }
        }

        /**
         * BC的SM3withSM2签名得到的结果的rs是asn1格式的，这个方法转化成直接拼接r||s
         * @param rsDer rs in asn1 format
         * @return sign result in plain byte array
         */
        private static byte[] rsAsn1ToPlainByteArray(byte[] rsDer)
        {
            Asn1Sequence seq = Asn1Sequence.GetInstance(rsDer);
            byte[] r = bigIntToFixexLengthBytes(DerInteger.GetInstance(seq[0]).Value);
            byte[] s = bigIntToFixexLengthBytes(DerInteger.GetInstance(seq[1]).Value);
            byte[] result = new byte[RS_LEN * 2];
            Buffer.BlockCopy(r, 0, result, 0, r.Length);
            Buffer.BlockCopy(s, 0, result, RS_LEN, s.Length);
            return result;
        }

        /**
         * BC的SM3withSM2验签需要的rs是asn1格式的，这个方法将直接拼接r||s的字节数组转化成asn1格式
         * @param sign in plain byte array
         * @return rs result in asn1 format
         */
        private static byte[] rsPlainByteArrayToAsn1(byte[] sign)
        {
            if (sign.Length != RS_LEN * 2) throw new ArgumentException("err rs. ");
            BigInteger r = new BigInteger(1, Arrays.CopyOfRange(sign, 0, RS_LEN));
            BigInteger s = new BigInteger(1, Arrays.CopyOfRange(sign, RS_LEN, RS_LEN * 2));
            Asn1EncodableVector v = new Asn1EncodableVector();
            v.Add(new DerInteger(r));
            v.Add(new DerInteger(s));
            try
            {
                return new DerSequence(v).GetEncoded("DER");
            }
            catch (IOException e)
            {
                //log.Error("RsPlainByteArrayToAsn1 error: " + e.Message, e);
                return null;
            }
        }
    }
}

此处为签名及验签 Demo

string PrivateKey = "AJciGDkPWcwX"; // 私钥，用于加签，此处是乱写的
string PublicKey = "BFaPS+Hj3eXg4ENOXDjrpLhwNIY";  // 公钥，与私钥配对，此处是乱写的

string userId = "";
string str = "TestContent";
//对字符串签名
byte[] signByte = EasyGmUtil.signSm3WithSm2(Encoding.UTF8.GetBytes(str), 
                  Encoding.UTF8.GetBytes(userId),  Org.BouncyCastle.Utilities.Encoders.Base64.Decode(PrivateKey));
string signStr =  Org.BouncyCastle.Utilities.Encoders.Base64.ToBase64String(signByte);

//验签
bool flag = EasyGmUtil.verifySm3WithSm2(Encoding.UTF8.GetBytes(str), Encoding.UTF8.GetBytes(userId),  
            Org.BouncyCastle.Utilities.Encoders.Base64.Decode(signStr),  
            Org.BouncyCastle.Utilities.Encoders.Base64.Decode(PublicKey));