c# - 使用 BouncyCaSTLe 验证 ECDSA 签名

Question

我正在测试 BouncyCaSTLe 以使用 ECDSA、nist P251 验证签名。(Xamarin 的加密 API 还没有实现，我开始使用 Bouncy CaSTLe lib。)

无论如何，我面对下面的代码，是...方法 B 与 C# API 一起正常工作，方法 A 则不然。A方法的ECPoint看起来有问题，但我无法检查细节。

(我有 checked ，但无法修复。)

我应该如何更改 A 方法？欢迎任何想法。提前致谢。

using Org.BouncyCastle.Asn1;
using Org.BouncyCastle.Asn1.Nist;
using Org.BouncyCastle.Asn1.X9;
using Org.BouncyCastle.Crypto.Parameters;
using Org.BouncyCastle.Math;
using Org.BouncyCastle.Math.EC;
using Org.BouncyCastle.Security;
using Org.BouncyCastle.Utilities.Encoders;
using System;
using System.Linq;
using System.Security.Cryptography;
using System.Text;

namespace TestMe
{
    class Program
    {

        public static byte[] HexStringToByteArray(string Hex)
        {
            byte[] Bytes = new byte[Hex.Length / 2];
            int[] HexValue = new int[] { 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09,
                                 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x0A, 0x0B, 0x0C, 0x0D,
                                 0x0E, 0x0F };

            for (int x = 0, i = 0; i < Hex.Length; i += 2, x += 1)
            {
                Bytes[x] = (byte)(HexValue[Char.ToUpper(Hex[i + 0]) - '0'] << 4 |
                                  HexValue[Char.ToUpper(Hex[i + 1]) - '0']);
            }

            return Bytes;
        }

        static void Main(string[] args)
        {
            String sig
                = "e1f5cecccedfe5228d9331098e84b69a0675cdd9ac066ecfada7fea761f52a4cde902a0abd362883127230326fb556af14e894d39a3e14437aaa4134a3476c84";

            String msg = "00000000dcb320137ddd6f825660750ab655219fad66951c64f0420be8ac902975197ed2b0da54cd3d502d34dd04c8d74b2958a0b8792ae4730df6d25a6969bcad9f93a7d6229e5a0100000017cf5242732bba21a0b0e7dad7102cf7bdb2c8d7a665045816a886d7";
            String pub = "b679e27513e2fff8fdeb54409c242776f3517f370440d26885de574a0b0e5309a9de4ea055b0bf302d9f00875f80e28cd29bb95a48aa53746d7de9465123dbb7";


            A(HexStringToByteArray(msg), HexStringToByteArray(sig), HexStringToByteArray(pub));
            B(HexStringToByteArray(msg), HexStringToByteArray(sig), HexStringToByteArray(pub));

        }

        //incorrect
        static void A(byte[] message, byte[] signature, byte[] pubkey)
        {            
            BigInteger x = new BigInteger(1, pubkey.Take(32).ToArray());
            BigInteger y = new BigInteger(1, pubkey.Skip(32).ToArray());

            X9ECParameters ecParams = NistNamedCurves.GetByName("P-256");
            ECDomainParameters domainParameters = new ECDomainParameters(ecParams.Curve, ecParams.G, ecParams.N, ecParams.H, ecParams.GetSeed());
            var G = ecParams.G;
            Org.BouncyCastle.Math.EC.ECCurve curve = ecParams.Curve;
            Org.BouncyCastle.Math.EC.ECPoint q = curve.CreatePoint(x, y);

            ECPublicKeyParameters pubkeyParam = new ECPublicKeyParameters(q, domainParameters);

            var verifier = SignerUtilities.GetSigner("SHA-256withECDSA");
            verifier.Init(false, pubkeyParam);
            verifier.BlockUpdate(message, 0, message.Length);
            bool result = verifier.VerifySignature(signature);

            Console.WriteLine("result: "  + result);
        }


        // correct
        static void B(byte[] message, byte[] signature, byte[] pubkey)
        {
            var Q = new System.Security.Cryptography.ECPoint();
            var param = new ECParameters();
            Q.X = pubkey.Take(32).ToArray();
            Q.Y = pubkey.Skip(32).ToArray();
            param.Curve = System.Security.Cryptography.ECCurve.NamedCurves.nistP256;
            param.Q = Q;            

            var ecdsa = ECDsa.Create(param);
            bool result = ecdsa.VerifyData(message, signature, HashAlgorithmName.SHA256);
            Console.WriteLine("result: " + result);
        }


    }
}

Answer 1

您使用充气城堡验证签名的代码是正确的。问题出在签名格式上。

ECDSA 签名基本上是两个数字，通常称为r 和s。在您示例的签名中，这两个数字只是连接在一起。它们每个都是 32 字节，所以你的签名是 64 字节。

这种格式(串联的数字)是 .NET api 所期望的，而不是 Bouncy CaSTLe 所期望的。 Bouncy CaSTLe 期望签名采用 DER 编码(就像规范规定的那样)。

因此您需要将签名从当前格式“转换”为 BC 期望的格式，如下所示:

// expected format is SEQUENCE {INTEGER r, INTEGER s}
var derSignature = new DerSequence(
    // first 32 bytes is "r" number
    new DerInteger(new BigInteger(1, signature.Take(32).ToArray())),
    // last 32 bytes is "s" number
    new DerInteger(new BigInteger(1, signature.Skip(32).ToArray())))
    .GetDerEncoded();

然后验证这个签名(顺便说一下现在是70字节):

bool result = verifier.VerifySignature(derSignature);

它会正常工作。