如何实现 可逆加密

Question

System.Security.Cryptography
有一堆加密算法可以用.
比如RSA,DES,AES之类的...

Answer 1

base64加密，解密using System;
using System.Data;
using System.Configuration;
using System.Linq;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Xml.Linq;/// <summary>
///Base64Encoder 的摘要说明
/// </summary>
public class Base64Encoder
{
    byte[] source;
    int length, length2;
    int blockCount;
    int paddingCount;
    public static Base64Encoder Encoder = new Base64Encoder();    public Base64Encoder()
    {
    }    private void init(byte[] input)
    {
        source = input;
        length = input.Length;
        if ((length % 3) == 0)
        {
            paddingCount = 0;
            blockCount = length / 3;
        }
        else
        {
            paddingCount = 3 - (length % 3);
            blockCount = (length + paddingCount) / 3;
        }
        length2 = length + paddingCount;
    }    public string GetEncoded(byte[] input)
    {
        //初始化
        init(input);        byte[] source2;
        source2 = new byte[length2];        for (int x = 0; x < length2; x++)
        {
            if (x < length)
            {
                source2[x] = source[x];
            }
            else
            {
                source2[x] = 0;
            }
        }        byte b1, b2, b3;
        byte temp, temp1, temp2, temp3, temp4;
        byte[] buffer = new byte[blockCount * 4];
        char[] result = new char[blockCount * 4];
        for (int x = 0; x < blockCount; x++)
        {
            b1 = source2[x * 3];
            b2 = source2[x * 3 + 1];
            b3 = source2[x * 3 + 2];            temp1 = (byte)((b1 & 252) >> 2);            temp = (byte)((b1 & 3) << 4);
            temp2 = (byte)((b2 & 240) >> 4);
            temp2 += temp;            temp = (byte)((b2 & 15) << 2);
            temp3 = (byte)((b3 & 192) >> 6);
            temp3 += temp;            temp4 = (byte)(b3 & 63);            buffer[x * 4] = temp1;
            buffer[x * 4 + 1] = temp2;
            buffer[x * 4 + 2] = temp3;
            buffer[x * 4 + 3] = temp4;        }        for (int x = 0; x < blockCount * 4; x++)
        {
            result[x] = sixbit2char(buffer[x]);
        }
        switch (paddingCount)
        {
            case 0: break;
            case 1: result[blockCount * 4 - 1] = '='; break;
            case 2: result[blockCount * 4 - 1] = '=';
                result[blockCount * 4 - 2] = '=';
                break;
            default: break;
        }
        return new string(result);
    }
    private char sixbit2char(byte b)
    {
        char[] lookupTable = new char[64]{
                  'A','B','C','D','E','F','G','H','I','J','K','L','M',
                 'N','O','P','Q','R','S','T','U','V','W','X','Y','Z',
                 'a','b','c','d','e','f','g','h','i','j','k','l','m',
                 'n','o','p','q','r','s','t','u','v','w','x','y','z',
                 '0','1','2','3','4','5','6','7','8','9','+','/'};        if ((b >= 0) && (b <= 63))
        {
            return lookupTable[(int)b];
        }
        else
        {            return ' ';
        }
    }}
using System;
using System.Data;
using System.Configuration;
using System.Linq;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Xml.Linq;/// <summary>
///Base64Decoder 的摘要说明
/// </summary>
public class Base64Decoder
{
char[] source;
        int length, length2, length3;
        int blockCount;
        int paddingCount;
        public static Base64Decoder Decoder = new Base64Decoder();        public Base64Decoder()
        {
        }        private void init(char[] input)
        {
            int temp = 0;
            source = input;
            length = input.Length;            for (int x = 0; x < 2; x++)
            {
                if (input[length - x - 1] == '=')
                    temp++;
            }
            paddingCount = temp;            blockCount = length / 4;
            length2 = blockCount * 3;
        }        public byte[] GetDecoded(string strInput)
        {
            //初始化
            init(strInput.ToCharArray());            byte[] buffer = new byte[length];
            byte[] buffer2 = new byte[length2];            for (int x = 0; x < length; x++)
            {
                buffer[x] = char2sixbit(source[x]);
            }            byte b, b1, b2, b3;
            byte temp1, temp2, temp3, temp4;            for (int x = 0; x < blockCount; x++)
            {
                temp1 = buffer[x * 4];
                temp2 = buffer[x * 4 + 1];
                temp3 = buffer[x * 4 + 2];
                temp4 = buffer[x * 4 + 3];                b = (byte)(temp1 << 2);
                b1 = (byte)((temp2 & 48) >> 4);
                b1 += b;                b = (byte)((temp2 & 15) << 4);
                b2 = (byte)((temp3 & 60) >> 2);
                b2 += b;                b = (byte)((temp3 & 3) << 6);
                b3 = temp4;
                b3 += b;                buffer2[x * 3] = b1;
                buffer2[x * 3 + 1] = b2;
                buffer2[x * 3 + 2] = b3;
            }            length3 = length2 - paddingCount;
            byte[] result = new byte[length3];            for (int x = 0; x < length3; x++)
            {
                result[x] = buffer2[x];
            }            return result;
        }        private byte char2sixbit(char c)
        {
            char[] lookupTable = new char[64]{ 
                 'A','B','C','D','E','F','G','H','I','J','K','L','M','N',
                 'O','P','Q','R','S','T','U','V','W','X','Y', 'Z',
                 'a','b','c','d','e','f','g','h','i','j','k','l','m','n',
                 'o','p','q','r','s','t','u','v','w','x','y','z',
                 '0','1','2','3','4','5','6','7','8','9','+','/'};
            if (c == '=')
                return 0;
            else
            {
                for (int x = 0; x < 64; x++)
                {
                    if (lookupTable[x] == c)
                        return (byte)x;
                }                return 0;
            }        }
    //解码类结束}

Answer 2

想可逆就能可逆，凯撒、异或、DES等都是可逆的。
好像不可逆比可逆难，而且还要兼顾密文的唯一性。

Answer 3

自己写，可逆公式: X -> KEY = Y

Answer 4

DES算法
        #region   对数据进行加密
        /// <summary>
        /// 对数据进行加密
        /// </summary>
        /// <param name="encryptstring">需要加密的数据</param>
        /// <returns></returns>
        public string DESEncrypt(string encryptstring)
        {
            string strRtn;
            try
            {
                DESCryptoServiceProvider desc = new DESCryptoServiceProvider();//des进行加密
                byte[] key = System.Text.Encoding.Unicode.GetBytes(encryptkey);
                byte[] data = System.Text.Encoding.Unicode.GetBytes(encryptstring);
                MemoryStream ms = new MemoryStream();//存储加密后的数据
                CryptoStream cs = new CryptoStream(ms, desc.CreateEncryptor(key, key), CryptoStreamMode.Write);
                cs.Write(data, 0, data.Length);//进行加密
                cs.FlushFinalBlock();
                strRtn = Convert.ToBase64String(ms.ToArray());
                return strRtn;
            }            catch (Exception ex)
            {
                MessageBox.Show("错误：" + ex.Message, "错误消息提示框", MessageBoxButtons.OKCancel, MessageBoxIcon.Error);
                return null;
            }
        }
        #endregion
 #region   对数据进行解密
        /// <summary>
        /// 对数据进行解密
        /// </summary>
        /// <param name="decryptstring">需要解密的数据</param>
        /// <returns></returns>
        public string DESDecrypt(string decryptstring)
        {
string strRtn;
            try
            {
                DESCryptoServiceProvider desc = new DESCryptoServiceProvider();
                byte[] key = System.Text.Encoding.Unicode.GetBytes(encryptkey);
                byte[] data = Convert.FromBase64String(decryptstring);
                MemoryStream ms = new MemoryStream();//存储解密后的数据
                CryptoStream cs = new CryptoStream(ms, desc.CreateDecryptor(key, key), CryptoStreamMode.Write);
                cs.Write(data, 0, data.Length);//解密数据
                cs.FlushFinalBlock();
                strRtn = System.Text.Encoding.Unicode.GetString(ms.ToArray());
                return strRtn;
            }
            catch (Exception ex)
            {
                MessageBox.Show("错误：" + ex.Message, "错误消息提示框", MessageBoxButtons.OKCancel, MessageBoxIcon.Error);
                return null;
            }
        }
        #endregion

Answer 5

DES就可以参考http://blog.csdn.net/zgke/archive/2009/02/04/3862159.aspx

Answer 6

#region 3DES加密和解密 DES的第三版本
    /// <summary>
    /// 3DES一个加密的方法
    /// </summary>
    /// <param name="M_Value">要加密的字符串</param>
    /// <returns></returns>
    public static string Encrypt3DES(string M_Value)
    {     
        //构造一个对称算法
        SymmetricAlgorithm mCSP = new TripleDESCryptoServiceProvider();
        string M_sKey = "JEFHTWkrTAUXpfO8NJWXdGJIoQz0/Jfw";//密钥
        string M_sIV = "HrxSqiWlb+A=";//矢量
        ICryptoTransform ct;//
        MemoryStream ms=new MemoryStream();;
        CryptoStream cs;
        byte[] byt=Encoding.UTF8.GetBytes(M_Value);
        mCSP.Key= Convert.FromBase64String(M_sKey);
        mCSP.IV = Convert.FromBase64String(M_sIV);
        //指定加密的运算模式
        mCSP.Mode = System.Security.Cryptography.CipherMode.ECB;
        //获取或设置加密算法的填充模式
        mCSP.Padding = System.Security.Cryptography.PaddingMode.PKCS7;
        ct = mCSP.CreateEncryptor(mCSP.Key, mCSP.IV);
        cs = new CryptoStream(ms, ct, CryptoStreamMode.Write);
        cs.Write(byt, 0, byt.Length);
        cs.FlushFinalBlock();
        cs.Close();
        return Convert.ToBase64String(ms.ToArray());
    }
    /// <summary>
    /// 3DES一个解密的方法
    /// </summary>
    /// <param name="Value">要加密的字符串</param>
    /// <returns></returns>
    public static string Decrypt3DES(string M_Value)
    {
        //构造一个对称算法
        SymmetricAlgorithm mCSP = new TripleDESCryptoServiceProvider();
        string M_sKey = "JEFHTWkrTAUXpfO8NJWXdGJIoQz0/Jfw";//密钥
        string M_sIV = "HrxSqiWlb+A=";//矢量
        ICryptoTransform ct;
        MemoryStream ms=new MemoryStream();;
        CryptoStream cs;
        byte[] byt=Convert.FromBase64String(M_Value);
        mCSP.Key = Convert.FromBase64String(M_sKey);
        mCSP.IV = Convert.FromBase64String(M_sIV);
        mCSP.Mode = System.Security.Cryptography.CipherMode.ECB;
        mCSP.Padding = System.Security.Cryptography.PaddingMode.PKCS7;
        ct = mCSP.CreateDecryptor(mCSP.Key, mCSP.IV);
        cs = new CryptoStream(ms, ct, CryptoStreamMode.Write);
        cs.Write(byt, 0, byt.Length);
        cs.FlushFinalBlock();
        cs.Close();
        return Encoding.UTF8.GetString(ms.ToArray());
    }    #endregion

Answer 7

N多加解密，参考：
http://www.cnblogs.com/lem-worm/archive/2007/09/04/881257.html