RSA使用

RSA使用

今天在跟同事一起调试TCP通讯的时候，在RSA私钥解密这块，着实让我费了一番心思。

流程大致是这样的，终端登录的时候使用固定的des密码加密数据发送，平台接收后确认登录信息后，会返回一个字符串，

该字符串是使用rsa公钥加密的一个字符串，作为后续通讯时使用的des密码。平台是使用JAVA开发的，该私钥和公钥文件会

在终端存一份。但是该文件是pem格式的，而且公钥使用证书的方式，调试使用公钥加密后的发送给平台，平台都是可以解密的。

但是平台发送回来的公钥加密就是解密不正常。其中查找资料就不多说了，总算是解决了。这里做一个记录，也做个分享。

其中使用到一个第三方库：BouncyCastle,可以使用NuGet来安装.

首先是RSA密钥与Pem密钥的互转。

/// <summary>
        /// Pem密钥转RSA密钥
        /// </summary>
        /// <param name="pemKey">Pem密钥</param>
        /// <param name="isPrivateKey">是否是私钥</param>
        /// <returns>RSA密钥</returns>
        public static string PemToRSAKey(string pemKeyFileName, bool isPrivateKey)
        {
            string rsaKey = string.Empty;
            object pemObject = null;
            RSAParameters rsaPara = new RSAParameters();
            using (StreamReader sReader = new StreamReader(pemKeyFileName))
            {
                var pemReader = new Org.BouncyCastle.OpenSsl.PemReader(sReader);
                pemObject = pemReader.ReadObject();

            }
            //RSA私钥
            if (isPrivateKey)
            {
                RsaPrivateCrtKeyParameters key = (RsaPrivateCrtKeyParameters)pemObject;
                rsaPara = new RSAParameters
                {
                    Modulus = key.Modulus.ToByteArrayUnsigned(),
                    Exponent = key.PublicExponent.ToByteArrayUnsigned(),
                    D = key.Exponent.ToByteArrayUnsigned(),
                    P = key.P.ToByteArrayUnsigned(),
                    Q = key.Q.ToByteArrayUnsigned(),
                    DP = key.DP.ToByteArrayUnsigned(),
                    DQ = key.DQ.ToByteArrayUnsigned(),
                    InverseQ = key.QInv.ToByteArrayUnsigned(),
                };
            }
            //RSA公钥
            else
            {
                RsaKeyParameters key = (RsaKeyParameters)pemObject;
                rsaPara = new RSAParameters
                {
                    Modulus = key.Modulus.ToByteArrayUnsigned(),
                    Exponent = key.Exponent.ToByteArrayUnsigned(),
                };
            }
            RSACryptoServiceProvider rsa = new RSACryptoServiceProvider();
            rsa.ImportParameters(rsaPara);
            using (StringWriter sw = new StringWriter())
            {
                sw.Write(rsa.ToXmlString(isPrivateKey ? true : false));
                rsaKey = sw.ToString();
            }
            return rsaKey;
        }
        /// <summary>
        /// RSA密钥转Pem密钥
        /// </summary>
        /// <param name="RSAKey">RSA密钥</param>
        /// <param name="isPrivateKey">是否是私钥</param>
        /// <returns>Pem密钥</returns>
        public static string RSAKeyToPem(string RSAKey, bool isPrivateKey)
        {
            string pemKey = string.Empty;
            RSACryptoServiceProvider rsa = new RSACryptoServiceProvider();
            rsa.FromXmlString(RSAKey);
            RSAParameters rsaPara = new RSAParameters();
            RsaKeyParameters key = null;
            //RSA私钥
            if (isPrivateKey)
            {
                rsaPara = rsa.ExportParameters(true);
                key = new RsaPrivateCrtKeyParameters(
                    new BigInteger(1, rsaPara.Modulus), new BigInteger(1, rsaPara.Exponent), new BigInteger(1, rsaPara.D),
                    new BigInteger(1, rsaPara.P), new BigInteger(1, rsaPara.Q), new BigInteger(1, rsaPara.DP), new BigInteger(1, rsaPara.DQ),
                    new BigInteger(1, rsaPara.InverseQ));
            }
            //RSA公钥
            else
            {
                rsaPara = rsa.ExportParameters(false);
                key = new RsaKeyParameters(false,
                    new BigInteger(1, rsaPara.Modulus),
                    new BigInteger(1, rsaPara.Exponent));
            }
            using (TextWriter sw = new StringWriter())
            {
                var pemWriter = new PemWriter(sw);
                pemWriter.WriteObject(key);
                pemWriter.Writer.Flush();
                pemKey = sw.ToString();
            }
            return pemKey;
        }

公钥加密,以证书方式打开pem密钥文件

 /// <summary>
/// RSA公钥加密
/// </summary>
/// <param name="data"></param>
/// <param name="publicKey"></param>
/// <returns></returns>
public static byte[] RSAPublicEncrypt(byte[] data, string publicKeyFileName)
{
    X509Certificate2 x509Certificate2 = new X509Certificate2(publicKeyFileName);
    RSACryptoServiceProvider pubKey = (RSACryptoServiceProvider)x509Certificate2.PublicKey.Key;
    byte[] bys = pubKey.Encrypt(data, false);
    //string result = Convert.ToBase64String(bys);
    //return Encoding.UTF8.GetBytes(result);
    return bys;
}

私钥解密

 /// <summary>
/// RSA私钥解密
/// </summary>
/// <param name="data"></param>
/// <param name="privateKey"></param>
/// <returns></returns>
public static byte[] RSAPrivateDecrypt(byte[] data, string privateKeyFileName)
{
    string xml = PemToRSAKey(privateKeyFileName, true);//将pem密钥转为RSA密钥
    RSACryptoServiceProvider rsa = new RSACryptoServiceProvider();
    rsa.FromXmlString(xml);
    return rsa.Decrypt(data, false);
}