前段时间将系统的RSA算法全部升级为SM2国密算法,密码机和UKey硬件设备大都同时支持RSA和SM2算法,只是应用系统的加解密签名验证需要修改,这个更改底层调用的加密动态库来,原来RSA用的对称加密算法DES(AES)和摘要MD5(SHA1)也相应改变,分别对应SM1、SM3算法,SM1算法基于硬件实现,SM2、SM3算法已公开。
SM2签名验证算法
SM2签名同样也是需要先摘要原文数据,即先使用SM3密码杂凑算法计算出32byte摘要。SM3需要摘要签名方ID(默认1234567812345678)、曲线参数a,b,Gx,Gy、共钥坐标(x,y)计算出Z值,然后再杂凑原文得出摘要数据。这个地方要注意曲线参数和坐标点都是32byte,在转换为BigInteger大数计算转成字节流时要去掉空补位,否则可能会出现摘要计算不正确的问题。SM2签名实现如下:
[java] view plaincopy
- public static BigInteger[] Sm2Sign(byte[] md, AsymmetricCipherKeyPair keypair)
- {
- SM3Digest sm3 = new SM3Digest();
- ECPublicKeyParameters ecpub = (ECPublicKeyParameters)keypair.Public;
- byte[] z = SM2CryptoServiceProvider.Sm2GetZ(Encoding.Default.GetBytes(SM2CryptoServiceProvider.userId), ecpub.Q);
- sm3.BlockUpdate(z, 0, z.Length);
- byte[] p = md;
- sm3.BlockUpdate(p, 0, p.Length);
- byte[] hashData = new byte[32];
- sm3.DoFinal(hashData, 0);
- // e
- BigInteger e = new BigInteger(1, hashData);
- // k
- BigInteger k = null;
- ECPoint kp = null;
- BigInteger r = null;
- BigInteger s = null;
- BigInteger userD = null;
- do
- {
- do
- {
- ECPrivateKeyParameters ecpriv = (ECPrivateKeyParameters)keypair.Private;
- k = ecpriv.D;
- kp = ecpub.Q;
- userD = ecpriv.D;
- // r
- r = e.Add(kp.X.ToBigInteger());
- r = r.Mod(ecc_n);
- }
- while (r.Equals(BigInteger.Zero) || r.Add(k).Equals(ecc_n));
- // (1 + dA)~-1
- BigInteger da_1 = userD.Add(BigInteger.One);
- da_1 = da_1.ModInverse(ecc_n);
- // s
- s = r.Multiply(userD);
- s = k.Subtract(s).Mod(ecc_n);
- s = da_1.Multiply(s).Mod(ecc_n);
- }
- while (s.Equals(BigInteger.Zero));
- byte[] btRS = new byte[64];
- byte[] btR = r.ToByteArray();
- byte[] btS = s.ToByteArray();
- Array.Copy(btR, btR.Length - 32, btRS, 0, 32);
- Array.Copy(btS, btS.Length - 32, btRS, 32, 32);
- return new BigInteger[] { r, s };
- }
SM2算法是基于ECC算法的,签名同样返回2个大数,共64byte。由于原来RSA算法已很普遍支持,要实现RSA的签名验签都有标准库的实现,而SM2是国密算法在国际上还没有标准通用,算法Oid标识在X509标准中是没定义的。在.Net或Java中可以基于使用BouncyCastle加密库实现,开源的也比较好学习扩展。SM2算法验签可以使用软验签,即可以不需要使用硬件设备,同样使用原始数据、签名、证书(公钥)来实现对签名方验证,保证数据完整性未被篡改。验证过程同样需先摘要原文数据,公钥在证书中是以一个66byte的BitString,去掉前面标记位即64byte为共钥坐标(x,y),中间分割截取再以Hex方式转成BigInteger大数计算,验签代码如下:
[java] view plaincopy
- public static bool Verify(byte[] msg, byte[] signData, byte[] certData)
- {
- X509Certificate2 x5092 = new X509Certificate2(certData);
- byte[] certPK = x5092.GetPublicKey();
- certPK = SubByte(certPK, 1, 64);
- byte[] certPKX = SubByte(certPK, certPK.Length - 32 - 32, 32);
- byte[] certPKY = SubByte(certPK, certPK.Length - 32, 32);
- System.String strcertPKX = ByteToHexStr(certPKX);
- System.String strcertPKY = ByteToHexStr(certPKY);
- BigInteger biX = new BigInteger(strcertPKX, 16);
- BigInteger biY = new BigInteger(strcertPKY, 16);
- ECFieldElement x = new FpFieldElement(ecc_p, biX);
- ECFieldElement y = new FpFieldElement(ecc_p, biY);
- ECPoint userKey = new FpPoint(ecc_curve, x, y);
- SM3Digest sm3 = new SM3Digest();
- byte[] z = Sm2GetZ(Encoding.Default.GetBytes(userId), userKey);
- sm3.BlockUpdate(z, 0, z.Length);
- byte[] p = msg;
- sm3.BlockUpdate(p, 0, p.Length);
- byte[] md = new byte[32];
- sm3.DoFinal(md, 0);
- byte[] btR = SubByte(signData, 0, 32);
- byte[] btS = SubByte(signData, 32, 32);
- System.String strR = ByteToHexStr(btR);
- System.String strS = ByteToHexStr(btS);
- BigInteger r = new BigInteger(strR, 16);
- BigInteger s = new BigInteger(strS, 16);
- // e_
- BigInteger e = new BigInteger(1, md);
- // t
- BigInteger t = r.Add(s).Mod(ecc_n);
- if (t.Equals(BigInteger.Zero))
- return false;
- // x1y1
- ECPoint x1y1 = ecc_point_g.Multiply(s);
- x1y1 = x1y1.Add(userKey.Multiply(t));
- // R
- BigInteger R = e.Add(x1y1.X.ToBigInteger()).Mod(ecc_n);
- return r.Equals(R);
- }
制作SM2证书
基于BouncyCastle开源库,可以轻松制作X509证书、CRL、pkcs10、pkcs12,支持国际通用的RSA、ECC算法。制作SM2证书可以通过扩展BouncyCastle库来实现,需加入SM2签名算法DerObjectIdentifier标识1.2.156.10197.1.501(基于SM3的SM2算法签名),密钥对的生成使用国密推荐曲线参数,然后如上所示自行实现SM2签名验证算法。X509证书由证书主体、证书签名算法标识、签名组成,和RSA证书主要不同的是SM2证书的签名算法标识和签名,及证书公钥使用ECKeyParameters。生成自签名SM2证书代码如下:
SM2证书生成
[java] view plaincopy
- public static Org.BouncyCastle.X509.X509Certificate MakeRootCert(string filePath, IDictionary subjectNames)
- {
- AsymmetricCipherKeyPair keypair = SM2CryptoServiceProvider.SM2KeyPairGenerator.GenerateKeyPair();
- ECPublicKeyParameters pubKey = (ECPublicKeyParameters)keypair.Public; //CA公钥
- ECPrivateKeyParameters priKey = (ECPrivateKeyParameters)keypair.Private; //CA私钥
- X509Name issuerDN = new X509Name(GetDictionaryKeys(subjectNames), subjectNames);
- X509Name subjectDN = issuerDN; //自签证书,两者一样
- SM2X509V3CertificateGenerator sm2CertGen = new SM2X509V3CertificateGenerator();
- //X509V3CertificateGenerator sm2CertGen = new X509V3CertificateGenerator();
- sm2CertGen.SetSerialNumber(new BigInteger(128, new Random())); //128位
- sm2CertGen.SetIssuerDN(issuerDN);
- sm2CertGen.SetNotBefore(DateTime.UtcNow.AddDays(-1));
- sm2CertGen.SetNotAfter(DateTime.UtcNow.AddDays(365 * 10));
- sm2CertGen.SetSubjectDN(subjectDN);
- sm2CertGen.SetPublicKey(pubKey); //公钥
- sm2CertGen.SetSignatureAlgorithm("SM3WITHSM2");
- sm2CertGen.AddExtension(X509Extensions.BasicConstraints, true, new BasicConstraints(true));
- sm2CertGen.AddExtension(X509Extensions.SubjectKeyIdentifier, false, new SubjectKeyIdentifierStructure(pubKey));
- sm2CertGen.AddExtension(X509Extensions.AuthorityKeyIdentifier, false, new AuthorityKeyIdentifierStructure(pubKey));
- sm2CertGen.AddExtension(X509Extensions.KeyUsage, true, new KeyUsage(6));
- Org.BouncyCastle.X509.X509Certificate sm2Cert = sm2CertGen.Generate(keypair);
- sm2Cert.CheckValidity();
- sm2Cert.Verify(pubKey);
- return sm2Cert;
- }
X509证书使用ASN1语法进行编码,是用类型标识、长度和值序列来描述数据结构的。SM2证书在制作设置公钥时,默认会带ECKeyParameters参数,并没有SM2的公钥参数1.2.156.10197.1.301,因此需要自己写个SM2椭圆曲线密码算法标识对象,这样在生成的证书中就可以看到公钥参数字段,如下所示:
SM2证书公钥标识
[java] view plaincopy
- using System;
- using Org.BouncyCastle.Asn1.X509;
- using Org.BouncyCastle.Asn1;
- namespace Common.Security
- {
- public class SM2AlgorithmIdentifier
- : AlgorithmIdentifier
- {
- private readonly bool parametersDefined;
- public SM2AlgorithmIdentifier(
- DerObjectIdentifier objectID):base(objectID)
- {
- }
- public SM2AlgorithmIdentifier(
- DerObjectIdentifier objectID,
- Asn1Encodable parameters)
- : base(objectID, parameters)
- {
- this.parametersDefined = true;
- }
- /**
- * Produce an object suitable for an Asn1OutputStream.
- * * AlgorithmIdentifier ::= Sequence {
- * algorithm OBJECT IDENTIFIER,
- * parameters ANY DEFINED BY algorithm OPTIONAL }
- *
- */
- public override Asn1Object ToAsn1Object()
- {
- DerObjectIdentifier sm2Identifier = new DerObjectIdentifier("1.2.156.10197.1.301");
- Asn1EncodableVector v = new Asn1EncodableVector(base.ObjectID, sm2Identifier);
- return new DerSequence(v);
- }
- }
- }
SM2算法是国密局公布的公钥密码算法,在相当强度下密钥比RSA短,在使用智能卡有限空间存储时非常可贵。目前国内很多CA大都升级支持SM2算法证书,相信以后会慢慢地推广更多应用,也期望之后能与国际标准接轨。
附:
国密推荐256位曲线参数
- p=FFFFFFFE FFFFFFFF FFFFFFFF FFFFFFFF FFFFFFFF 00000000 FFFFFFFF FFFFFFFF
- a=FFFFFFFE FFFFFFFF FFFFFFFF FFFFFFFF FFFFFFFF 00000000 FFFFFFFF FFFFFFFC
- b=28E9FA9E 9D9F5E34 4D5A9E4B CF6509A7 F39789F5 15AB8F92 DDBCBD41 4D940E93
- n=FFFFFFFE FFFFFFFF FFFFFFFF FFFFFFFF 7203DF6B 21C6052B 53BBF409 39D54123
- Gx=32C4AE2C 1F198119 5F990446 6A39C994 8FE30BBF F2660BE1 715A4589 334C74C7
- Gy=BC3736A2 F4F6779C 59BDCEE3 6B692153 D0A9877C C62A4740 02DF32E5 2139F0A0