C#实现SHA256WithRSA加密用于Java的秘钥私钥

首先要把Java秘钥进行转换，然后再进行加密

转制秘钥的方法

public static string RSAPrivateKeyJava2DotNet(string privateKey)
{
            RsaPrivateCrtKeyParameters privateKeyParam = (RsaPrivateCrtKeyParameters)PrivateKeyFactory.CreateKey(Convert.FromBase64String(privateKey));

            return string.Format("<RSAKeyValue><Modulus>{0}</Modulus><Exponent>{1}</Exponent><P>{2}</P><Q>{3}</Q><DP>{4}</DP><DQ>{5}</DQ><InverseQ>{6}</InverseQ><D>{7}</D></RSAKeyValue>",
                Convert.ToBase64String(privateKeyParam.Modulus.ToByteArrayUnsigned()),
                Convert.ToBase64String(privateKeyParam.PublicExponent.ToByteArrayUnsigned()),
                Convert.ToBase64String(privateKeyParam.P.ToByteArrayUnsigned()),
                Convert.ToBase64String(privateKeyParam.Q.ToByteArrayUnsigned()),
                Convert.ToBase64String(privateKeyParam.DP.ToByteArrayUnsigned()),
                Convert.ToBase64String(privateKeyParam.DQ.ToByteArrayUnsigned()),
                Convert.ToBase64String(privateKeyParam.QInv.ToByteArrayUnsigned()),
                Convert.ToBase64String(privateKeyParam.Exponent.ToByteArrayUnsigned()));
}

加密的方法

public static string Sign(string contentForSign, string privateKey)
        {
            //转换成适用于.Net的秘钥
            var netKey = RSAPrivateKeyJava2DotNet(privateKey);
            var rsa = new RSACryptoServiceProvider();
            rsa.FromXmlString(netKey);
            //创建一个空对象
            var rsaClear = new RSACryptoServiceProvider();
            var paras = rsa.ExportParameters(true);
            rsaClear.ImportParameters(paras);
            //签名返回
            using (var sha256 = new SHA256CryptoServiceProvider())
            {
                var signData = rsa.SignData(Encoding.UTF8.GetBytes(contentForSign), sha256);
                return BytesToHex(signData);
            }
        } 

public static string BytesToHex(byte[] data)
{
            StringBuilder sbRet = new StringBuilder(data.Length * 2);
            for (int i = 0; i < data.Length; i++)
            {
                sbRet.Append(Convert.ToString(data[i], 16).PadLeft(2, '0'));
            }
            return sbRet.ToString();
}

调用：

string rsaSecret = @"MIIBUwIBADANBgkqhkiG9w0BAQEFAASCAT0wggE5AgEAAkEAjdAhDuqzKCzaYyrrxFLdWVoR7wwmSdbVHBSZ/lpILvN/vPaohbi0NChwAEXYbvIXrFQ7zQyuqKazoEbvvXRNKQ.......";

string signDataString = Sign("Hello World!", rsaSecret);