C# 使用 MD5, DES, RSA 演算法加解密

http://richielin-programer.blogspot.com/2008/04/c-md5-des-rsa.html

在 .NET Framework 中有個 namespace 是專門處理加解密動作
System.Security.Cryptography
針對許多種加解密方式都有對應的類別來處理
天秤列出三種加密法實作
其它加密碼如 SHA1 系列與 MD5 語法相似，AES 與 DES 語法相似
就不另外寫出來了
PS. 以下部份資料取至 維基百科

MD5 演算法

MD5 即 Message-Digest Algorithm 5，是電腦廣泛使用的雜湊演算法之一
其演算法複雜度和不可逆性，通常用於確保資訊傳輸完整一致
因其不可逆性，所以只有加密的函式，沒有解密的函式

/// <summary> <BR> /// 取得 MD5 編碼後的 Hex 字串 <BR> /// 加密後為 32 Bytes Hex String (16 Byte) <BR> /// </summary> <BR> /// <param name="original">原始字串</param> <BR> /// <returns></returns> <BR> public static string GetMD5(string original) <BR> { <BR> MD5CryptoServiceProvider md5 = new MD5CryptoServiceProvider(); <BR> byte[] b = md5.ComputeHash(Encoding.UTF8.GetBytes(original)); <BR> return BitConverter.ToString(b).Replace("-", string.Empty); <BR> }

DES 加解密演算法

DES 加密法於 1977 年被聯邦政府列為數據加密標準
其加解密速度非常快速，但因為 56 位元金鑰過短
很有可能於 24 小時內被破解
如果需要安全一點的加密方式，可以考慮改用 AES 機制
AES 語法與 DES 大致相同，只在加解密的金鑰 KEY 及 IV 長度不同
加密及解碼需使用相同的金鑰

/// <summary> <BR> /// DES 加密字串 <BR> /// </summary> <BR> /// <param name="original">原始字串</param> <BR> /// <param name="key">Key，長度必須為 8 個 ASCII 字元</param> <BR> /// <param name="iv">IV，長度必須為 8 個 ASCII 字元</param> <BR> /// <returns></returns> <BR> public static string EncryptDES(string original, string key, string iv) <BR> { <BR> try <BR> { <BR> DESCryptoServiceProvider des = new DESCryptoServiceProvider(); <BR> des.Key = Encoding.ASCII.GetBytes(key); <BR> des.IV = Encoding.ASCII.GetBytes(iv); <BR> byte[] s = Encoding.ASCII.GetBytes(original); <BR> ICryptoTransform desencrypt = des.CreateEncryptor(); <BR> return BitConverter.ToString(desencrypt.TransformFinalBlock(s, 0, s.Length)).Replace("-", string.Empty); <BR> } <BR> catch { return original; } <BR> } <BR> <BR> /// <summary> <BR> /// DES 解密字串 <BR> /// </summary> <BR> /// <param name="hexString">加密後 Hex String</param> <BR> /// <param name="key">Key，長度必須為 8 個 ASCII 字元</param> <BR> /// <param name="iv">IV，長度必須為 8 個 ASCII 字元</param> <BR> /// <returns></returns> <BR> public static string DecryptDES(string hexString, string key, string iv) <BR> { <BR> try <BR> { <BR> DESCryptoServiceProvider des = new DESCryptoServiceProvider(); <BR> des.Key = Encoding.ASCII.GetBytes(key); <BR> des.IV = Encoding.ASCII.GetBytes(iv); <BR> <BR> byte[] s = new byte[hexString.Length / 2]; <BR> int j = 0; <BR> for (int i = 0; i < hexString.Length/2; i++) <BR> { <BR> s[i] = Byte.Parse(hexString[j].ToString() + hexString[j + 1].ToString(), System.Globalization.NumberStyles.HexNumber); <BR> j += 2; <BR> } <BR> ICryptoTransform desencrypt = des.CreateDecryptor(); <BR> return Encoding.ASCII.GetString(desencrypt.TransformFinalBlock(s, 0, s.Length)); <BR> } <BR> catch { return hexString; } <BR> } <BR>

RSA 加解密演算法

RSA 是一種非對稱性加密演算法，其原理是以公鑰及私鑰來處理加解密
簡單來說，公鑰可以提供給任何需要加密的人，但是私鑰必須妥善保存
加密時以公鑰處理即可，但解密必須有私鑰

在 .NET Framework 中公私鑰可以 xml 及 RSAParameters 類別型態存在
而金鑰產生最簡單的方式是由 RSACryptoServiceProvider 類別來產生
每次初始化 RSACryptoServiceProvider 類別時即會亂數產生一組金鑰

RSACryptoServiceProvider rsa = new RSACryptoServiceProvider(); <BR> // 公鑰 xml 字串 <BR> publicXml = rsa.ToXmlString(false); <BR> // 私鑰 xml 字串 <BR> privateXml = rsa.ToXmlString(true); <BR> // 公鑰 <BR> publicParameter = rsa.ExportParameters(false); <BR> // 私鑰 <BR> privateParameter = rsa.ExportParameters(true); <BR>

加解密時只要使用同一組金鑰 (公私鑰) 即可

/// <summary> <BR> /// RSA 加密字串 <BR> /// </summary> <BR> /// <param name="original">原始字串</param> <BR> /// <param name="xmlString">公鑰 xml 字串</param> <BR> /// <returns></returns> <BR> public static string EncryptRSA(string original, string xmlString) <BR> { <BR> try <BR> { <BR> RSACryptoServiceProvider rsa = new RSACryptoServiceProvider(); <BR> rsa.FromXmlString(xmlString); <BR> byte[] s = Encoding.ASCII.GetBytes(original); <BR> return BitConverter.ToString(rsa.Encrypt(s, false)).Replace("-", string.Empty); <BR> } <BR> catch { return original; } <BR> } <BR> <BR> /// <summary> <BR> /// RSA 加密字串 <BR> /// 加密後為 256 Bytes Hex String (128 Byte) <BR> /// </summary> <BR> /// <param name="original">原始字串</param> <BR> /// <param name="parameters">公鑰 RSAParameters 類別</param> <BR> /// <returns></returns> <BR> public static string EncryptRSA(string original, RSAParameters parameters) <BR> { <BR> try <BR> { <BR> RSACryptoServiceProvider rsa = new RSACryptoServiceProvider(); <BR> rsa.ImportParameters(parameters); <BR> byte[] s = Encoding.ASCII.GetBytes(original); <BR> return BitConverter.ToString(rsa.Encrypt(s, false)).Replace("-", string.Empty); <BR> } <BR> catch { return original; } <BR> } <BR> <BR> /// <summary> <BR> /// RSA 解密字串 <BR> /// </summary> <BR> /// <param name="hexString">加密後 Hex String</param> <BR> /// <param name="xmlString">私鑰 xml 字串</param> <BR> /// <returns></returns> <BR> public static string DecryptRSA(string hexString, string xmlString) <BR> { <BR> try <BR> { <BR> RSACryptoServiceProvider rsa = new RSACryptoServiceProvider(); <BR> rsa.FromXmlString(xmlString); <BR> byte[] s = new byte[hexString.Length / 2]; <BR> int j = 0; <BR> for (int i = 0; i < hexString.Length/2; i++) <BR> { <BR> s[i] = Byte.Parse(hexString[j].ToString() + hexString[j + 1].ToString(), System.Globalization.NumberStyles.HexNumber); <BR> j += 2; <BR> } <BR> return Encoding.ASCII.GetString(rsa.Decrypt(s, false)); <BR> } <BR> catch { return hexString; } <BR> } <BR> <BR> /// <summary> <BR> /// RSA 解密字串 <BR> /// </summary> <BR> /// <param name="hexString">加密後 Hex String</param> <BR> /// <param name="parameters">私鑰 RSAParameters 類別</param> <BR> /// <returns></returns> <BR> public static string DecryptRSA(string hexString, RSAParameters parameters) <BR> { <BR> try <BR> { <BR> RSACryptoServiceProvider rsa = new RSACryptoServiceProvider(); <BR> rsa.ImportParameters(parameters); <BR> byte[] s = new byte[hexString.Length / 2]; <BR> int j = 0; <BR> for (int i = 0; i < hexString.Length/2; i++) <BR> { <BR> s[i] = Byte.Parse(hexString[j].ToString() + hexString[j + 1].ToString(), System.Globalization.NumberStyles.HexNumber); <BR> j += 2; <BR> } <BR> return Encoding.ASCII.GetString(rsa.Decrypt(s, false)); <BR> } <BR> catch { return hexString; } <BR> } <BR>