using System;

using System.Text;

using System.Security.Cryptography;

using System.Web;

using System.IO;

namespace Thinhunan.Cnblogs.Com.RSAUtility

{

    public class PemConverter

    {

        /// <summary>

        /// 将pem格式公钥转换为RSAParameters

        /// </summary>

        /// <param name="pemFileConent">pem公钥内容</param>

        /// <returns>转换得到的RSAParamenters</returns>

        public static RSAParameters ConvertFromPemPublicKey(string pemFileConent)

        {

            if (string.IsNullOrEmpty(pemFileConent))

            {

                throw new ArgumentNullException("pemFileConent", "This arg cann't be empty.");

            }

            pemFileConent = pemFileConent.Replace("-----BEGIN PUBLIC KEY-----", "").Replace("-----END PUBLIC KEY-----", "").Replace("\n", "").Replace("\r", "");

            byte[] keyData = Convert.FromBase64String(pemFileConent);

            if (keyData.Length < 162)

            {

                throw new ArgumentException("pem file content is incorrect.");

            }

            byte[] pemModulus = new byte[128];

            byte[] pemPublicExponent = new byte[3];

            Array.Copy(keyData, 29, pemModulus, 0, 128);

            Array.Copy(keyData, 159, pemPublicExponent, 0, 3);

            RSAParameters para = new RSAParameters();

            para.Modulus = pemModulus;

            para.Exponent = pemPublicExponent;

            return para;

        }

        /// <summary>

        /// 将pem格式私钥转换为RSAParameters

        /// </summary>

        /// <param name="pemFileConent">pem私钥内容</param>

        /// <returns>转换得到的RSAParamenters</returns>

        public static RSAParameters ConvertFromPemPrivateKey(string pemFileConent)

        {

            if (string.IsNullOrEmpty(pemFileConent))

            {

                throw new ArgumentNullException("pemFileConent", "This arg cann't be empty.");

            }

            pemFileConent = pemFileConent.Replace("-----BEGIN RSA PRIVATE KEY-----", "").Replace("-----END RSA PRIVATE KEY-----", "").Replace("\n", "").Replace("\r","");

            byte[] keyData = Convert.FromBase64String(pemFileConent);

            if (keyData.Length < 609)

            {

                throw new ArgumentException("pem file content is incorrect.");

            }

            int index = 11;

            byte[] pemModulus = new byte[128];

            Array.Copy(keyData, index, pemModulus, 0, 128);

            index += 128;

            index += 2;//141

            byte[] pemPublicExponent = new byte[3];

            Array.Copy(keyData, index, pemPublicExponent, 0, 3);

            index += 3;

            index += 4;//148

            byte[] pemPrivateExponent = new byte[128];

            Array.Copy(keyData, index , pemPrivateExponent, 0, 128);

            index += 128;

            index += ((int)keyData[index+1] == 64?2: 3);//279

            byte[] pemPrime1 = new byte[64];

            Array.Copy(keyData, index, pemPrime1, 0, 64);

            index += 64;

            index += ((int)keyData[index + 1] == 64 ? 2 : 3);//346

            byte[] pemPrime2 = new byte[64];

            Array.Copy(keyData, index , pemPrime2, 0, 64);

            index += 64;

            index += ((int)keyData[index + 1] == 64 ? 2 : 3);//412/413

            byte[] pemExponent1 = new byte[64];

            Array.Copy(keyData,index, pemExponent1, 0, 64);

            index += 64;

            index += ((int)keyData[index + 1] == 64 ? 2 : 3);//479/480

            byte[] pemExponent2 = new byte[64];

            Array.Copy(keyData, index, pemExponent2, 0, 64);

            index += 64;

            index += ((int)keyData[index + 1] == 64 ? 2 : 3);//545/546

            byte[] pemCoefficient = new byte[64];

            Array.Copy(keyData, index, pemCoefficient, 0, 64);

            RSAParameters para = new RSAParameters();

            para.Modulus = pemModulus;

            para.Exponent = pemPublicExponent;

            para.D = pemPrivateExponent;

            para.P = pemPrime1;

            para.Q = pemPrime2;

            para.DP = pemExponent1;

            para.DQ = pemExponent2;

            para.InverseQ = pemCoefficient;

            return para;

        }

    }

}

测试pem导成RSAParameters成功，使用通过：

using System;

using System.Security.Cryptography;

using System.Text;

using System.IO;

using System.Web;

namespace Thinhunan.Cnblogs.Com.RSAUtility

{

    class Program

    {

        #region keys

        const string PUBLICKEY =

@"-----BEGIN PUBLIC KEY-----

MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQDpsDr+W45aFHIkvotZaGK/THlF

FpuZfUtghhWkHAm3H7yvL42J4xHrTr6IeUDCl4eKe6qiIgvYSNoL3u4SERGOeYmV

1F+cocu9IMGnNoicbh1zVW6e8/iGT3xaYQizJoVuWA/TC/zdds2ihCJfHDBDsouO

CXecPapyWCGQNsH5sQIDAQAB

-----END PUBLIC KEY-----";

        const string PRIVATEKEY =

@"-----BEGIN RSA PRIVATE KEY-----

MIICXQIBAAKBgQDpsDr+W45aFHIkvotZaGK/THlFFpuZfUtghhWkHAm3H7yvL42J

4xHrTr6IeUDCl4eKe6qiIgvYSNoL3u4SERGOeYmV1F+cocu9IMGnNoicbh1zVW6e

8/iGT3xaYQizJoVuWA/TC/zdds2ihCJfHDBDsouOCXecPapyWCGQNsH5sQIDAQAB

AoGBAM/JbFs4y5WbMncrmjpQj+UrOXVOCeLrvrc/4kQ+zgCvTpWywbaGWiuRo+cz

cXrVQ6bGGU362e9hr8f4XFViKemDL4SmJbgSDa1K71i+/LnnzF6sjiDBFQ/jA9SK

4PYrY7a3IkeBQnJmknanykugyQ1xmCjbuh556fOeRPaHnhx1AkEA/flrxJSy1Z+n

Y1RPgDOeDqyG6MhwU1Jl0yJ1sw3Or4qGRXhjTeGsCrKqV0/ajqdkDEM7FNkqnmsB

+vPd116J6wJBAOuNY3oOWvy2fQ32mj6XV+S2vcG1osEUaEuWvEgkGqJ9co6100Qp

j15036AQEEDqbjdqS0ShfeRSwevTJZIap9MCQCeMGDDjKrnDA5CfB0YiQ4FrchJ7

a6o90WdAHW3FP6LsAh59MZFmC6Ea0xWHdLPz8stKCMAlVNKYPRWztZ6ctQMCQQC8

iWbeAy+ApvBhhMjg4HJRdpNbwO6MbLEuD3CUrZFEDfTrlU2MeVdv20xC6ZiY3Qtq

/4FPZZNGdZcSEuc3km5RAkApGkZmWetNwDJMcUJbSBrQMFfrQObqMPBPe+gEniQq

Ttwu1OULHlmUg9eW31wRI2uiXcFCJMHuro6iOQ1VJ4Qs

-----END RSA PRIVATE KEY-----";

        #endregion

        static void Main(string[] args)

        {            

            TestSignAndVerify();

        }

        public static void TestSignAndVerify()

        {

            //sign

            RSAParameters para = PemConverter.ConvertFromPemPrivateKey(PRIVATEKEY);

            RSACryptoServiceProvider rsa = new RSACryptoServiceProvider();

            rsa.ImportParameters(para);

            byte[] testData = Encoding.UTF8.GetBytes("hello");

            MD5CryptoServiceProvider md5 = new MD5CryptoServiceProvider();

            byte[] signData = rsa.SignData(testData, md5);

            //verify

            RSAParameters paraPub = PemConverter.ConvertFromPemPublicKey(PUBLICKEY);

            RSACryptoServiceProvider rsaPub = new RSACryptoServiceProvider();

            rsaPub.ImportParameters(paraPub);

            if (rsaPub.VerifyData(testData, md5, signData))

            {

                Console.WriteLine("ok");

            }

            else

            {

                Console.WriteLine("no");

            }

        }

    }

}