using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Security.Cryptography;
using System.Text;
using System.Web;

namespace RSA
{
    class Signature
    {
        public static string PrivateKey
        {
            get
            {
                //此处为私钥文件的地址
                return @"XXXXXX";
            }
        }

        static void Main(string[] args)
        {
            var strSignature = string.Empty;//签名字符串
            var dict = new Dictionary<string, string>
            {
                {"key1", "value1"}, 
                {"key2", "value2"}
            };
            strSignature = SortByAscii(dict);

            var strCypherText = RSASign(strSignature);//签名完成后的字符串

            Console.WriteLine(strCypherText);
            Console.ReadKey();
        }

        public static string SortByAscii(Dictionary<string, string> paramsMap)
        {
            var vDic = (from objDic in paramsMap orderby objDic.Key ascending select objDic);
            var str = new StringBuilder();
            foreach (KeyValuePair<string, string> kv in vDic)
            {
                var pkey = System.Web.HttpUtility.UrlEncode(kv.Key);
                var pvalue = System.Web.HttpUtility.UrlEncode(kv.Value);
                str.Append(pkey + "=" + pvalue + "&");
            }

            return str.ToString().TrimEnd('&') + "," + ConvertDateTimeInt(DateTime.Now);
        }

        /// <summary>  
        /// DateTime时间格式转换为Unix时间戳格式  
        /// </summary>  
        /// <param name="time"> DateTime时间格式</param>  
        /// <returns>Unix时间戳格式</returns>  
        public static int ConvertDateTimeInt(System.DateTime time)
        {
            var startTime = TimeZone.CurrentTimeZone.ToLocalTime(new System.DateTime(1970, 1, 1));
            return (int)(time - startTime).TotalSeconds;
        }

        public static string RSASign(string data)
        {
            RSACryptoServiceProvider rsaCsp = LoadCertificateFile(PrivateKey);
            byte[] dataBytes = null;
            dataBytes = Encoding.UTF8.GetBytes(data);

            byte[] signatureBytes = rsaCsp.SignData(dataBytes, "SHA256");
            return Convert.ToBase64String(signatureBytes);
        }

        private static RSACryptoServiceProvider LoadCertificateFile(string filename)
        {
            using (System.IO.FileStream fs = System.IO.File.OpenRead(filename))
            {
                byte[] data = new byte[fs.Length];
                byte[] res = null;
                fs.Read(data, 0, data.Length);
                if (data[0] != 0x30)
                {
                    res = GetPem("RSA PRIVATE KEY", data);
                }
                try
                {
                    RSACryptoServiceProvider rsa = DecodeRSAPrivateKey(res);
                    return rsa;
                }
                catch
                {
                    throw;
                }
            }
        }

        private static byte[] GetPem(string type, byte[] data)
        {
            string pem = Encoding.UTF8.GetString(data);
            string header = String.Format("-----BEGIN {0}-----\\n", type);
            string footer = String.Format("-----END {0}-----", type);
            int start = pem.IndexOf(header) + header.Length;
            int end = pem.IndexOf(footer, start);
            string base64 = pem.Substring(start, (end - start));

            return Convert.FromBase64String(base64);
        }

        private static RSACryptoServiceProvider DecodeRSAPrivateKey(byte[] privkey)
        {
            byte[] MODULUS, E, D, P, Q, DP, DQ, IQ;

            // --------- Set up stream to decode the asn.1 encoded RSA private key ------
            MemoryStream mem = new MemoryStream(privkey);
            BinaryReader binr = new BinaryReader(mem);  //wrap Memory Stream with BinaryReader for easy reading
            byte bt = 0;
            ushort twobytes = 0;
            int elems = 0;
            try
            {
                twobytes = binr.ReadUInt16();
                if (twobytes == 0x8130) //data read as little endian order (actual data order for Sequence is 30 81)
                    binr.ReadByte();    //advance 1 byte
                else if (twobytes == 0x8230)
                    binr.ReadInt16();    //advance 2 bytes
                else
                    return null;

                twobytes = binr.ReadUInt16();
                if (twobytes != 0x0102) //version number
                    return null;
                bt = binr.ReadByte();
                if (bt != 0x00)
                    return null;


                //------ all private key components are Integer sequences ----
                elems = GetIntegerSize(binr);
                MODULUS = binr.ReadBytes(elems);

                elems = GetIntegerSize(binr);
                E = binr.ReadBytes(elems);

                elems = GetIntegerSize(binr);
                D = binr.ReadBytes(elems);

                elems = GetIntegerSize(binr);
                P = binr.ReadBytes(elems);

                elems = GetIntegerSize(binr);
                Q = binr.ReadBytes(elems);

                elems = GetIntegerSize(binr);
                DP = binr.ReadBytes(elems);

                elems = GetIntegerSize(binr);
                DQ = binr.ReadBytes(elems);

                elems = GetIntegerSize(binr);
                IQ = binr.ReadBytes(elems);


                // ------- create RSACryptoServiceProvider instance and initialize with public key -----
                CspParameters CspParameters = new CspParameters();
                CspParameters.Flags = CspProviderFlags.UseMachineKeyStore;

                int bitLen = 1024;

                RSACryptoServiceProvider RSA = new RSACryptoServiceProvider(bitLen, CspParameters);
                RSAParameters RSAparams = new RSAParameters();
                RSAparams.Modulus = MODULUS;
                RSAparams.Exponent = E;
                RSAparams.D = D;
                RSAparams.P = P;
                RSAparams.Q = Q;
                RSAparams.DP = DP;
                RSAparams.DQ = DQ;
                RSAparams.InverseQ = IQ;
                RSA.ImportParameters(RSAparams);
                return RSA;
            }
            catch (Exception ex)
            {
                return null;
            }
            finally
            {
                binr.Close();
            }
        }

        private static int GetIntegerSize(BinaryReader binr)
        {
            byte bt = 0;
            byte lowbyte = 0x00;
            byte highbyte = 0x00;
            int count = 0;
            bt = binr.ReadByte();
            if (bt != 0x02)     //expect integer
                return 0;
            bt = binr.ReadByte();

            if (bt == 0x81)
                count = binr.ReadByte();    // data size in next byte
            else
                if (bt == 0x82)
                {
                    highbyte = binr.ReadByte(); // data size in next 2 bytes
                    lowbyte = binr.ReadByte();
                    byte[] modint = { lowbyte, highbyte, 0x00, 0x00 };
                    count = BitConverter.ToInt32(modint, 0);
                }
                else
                {
                    count = bt;     // we already have the data size
                }

            while (binr.ReadByte() == 0x00)
            {   //remove high order zeros in data
                count -= 1;
            }
            binr.BaseStream.Seek(-1, SeekOrigin.Current);       //last ReadByte wasn't a removed zero, so back up a byte
            return count;
        }
    }
}