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  1. using System;
  2. using System.Text;
  3. using System.Security.Cryptography;
  4. using System.Linq;
  5.  
  6.  
  7. namespace Deckard.Jared
  8. {
  9.     /// <summary>
  10.     /// AES256 class uses the AES algorithm with a provided 256 bit key and a random 128 bit IV to meet PCI standards
  11.     /// The IV is randomly generated before each encryption and encoded with the final encrypted string
  12.     /// </summary>
  13.     public class AES256
  14.     {
  15.         // Symmetric algorithm interface is used to store the AES service provider
  16.         private SymmetricAlgorithm AESProvider;
  17.  
  18.         /// <summary>
  19.         /// Constructor for AES class that takes a byte array for the key
  20.         /// </summary>
  21.         /// <param name="key">256 bit key (32 bytes)</param>
  22.         public AES256(byte[] key)
  23.         {
  24.             // Throw error if key is not 256 bits
  25.             if (key.Length != 32) throw new CryptographicException("Key must be 256 bits (32 bytes)");
  26.  
  27.             // Initialize AESProvider with AES algorithm service
  28.             AESProvider = new AesCryptoServiceProvider();
  29.             AESProvider.KeySize = 256;
  30.  
  31.             // Set the key for AESProvider
  32.             AESProvider.Key = key;
  33.         }
  34.  
  35.         /// <summary>
  36.         /// Constructor for AES class that generates the key from a hashed, salted password
  37.         /// </summary>
  38.         /// <param name="password">Password used to generate the key (Minimum of 8 characters)</param>
  39.         /// <param name="salt">Salt used to secure hash from rainbow table attacks (Minimum of 8 characters)</param>
  40.         public AES256(string password, string salt)
  41.         {
  42.             // Throw error if the password or salt are too short
  43.             if (password.Length < 8) throw new CryptographicException("Password must be at least 8 characters long");
  44.             if (salt.Length < 8) throw new CryptographicException("Salt must be at least 8 characters long");
  45.  
  46.             // Initialize AESProvider with AES algorithm service
  47.             AESProvider = new AesCryptoServiceProvider();
  48.             AESProvider.KeySize = 256;
  49.  
  50.             // Initialize a hasher with the 256 bit SHA algorithm
  51.             SHA256 sha256 = System.Security.Cryptography.SHA256.Create();
  52.  
  53.             // Hash salted password
  54.             byte[] key = sha256.ComputeHash(UnicodeEncoding.Unicode.GetBytes(password + salt));
  55.  
  56.             // Set the key for AESProvider
  57.             AESProvider.Key = key;
  58.  
  59.         }
  60.  
  61.         /// <summary>
  62.         /// Encrypts a string with AES algorithm
  63.         /// </summary>
  64.         /// <param name="plainText">String to encrypt</param>
  65.         /// <returns>Encrypted string with IV prefix</returns>
  66.         public string Encrypt(string plainText)
  67.         {
  68.             // Create new random IV
  69.             AESProvider.GenerateIV();
  70.  
  71.             // Initialize encryptor now that the IV is set
  72.             ICryptoTransform encryptor = AESProvider.CreateEncryptor();
  73.  
  74.             // Convert string to bytes
  75.             byte[] plainBytes = UnicodeEncoding.Unicode.GetBytes(plainText);
  76.  
  77.             // Encrypt plain bytes
  78.             byte[] secureBytes = encryptor.TransformFinalBlock(plainBytes, 0, plainBytes.Length);
  79.  
  80.             // Add IV to the beginning of the encrypted bytes
  81.             secureBytes = AESProvider.IV.Concat(secureBytes).ToArray();
  82.  
  83.             // Return encrypted bytes as a string
  84.             return Convert.ToBase64String(secureBytes);
  85.         }
  86.  
  87.         /// <summary>
  88.         /// Decrypts a string with AES algorithm
  89.         /// </summary>
  90.         /// <param name="secureText">Encrypted string with IV prefix</param>
  91.         /// <returns>Decrypted string</returns>
  92.         public string Decrypt(string secureText)
  93.         {
  94.             // Convert encrypted string to bytes
  95.             byte[] secureBytes = Convert.FromBase64String(secureText);
  96.  
  97.             // Take IV from beginning of secureBytes
  98.             AESProvider.IV = secureBytes.Take(16).ToArray();
  99.  
  100.             // Initialize decryptor now that the IV is set
  101.             ICryptoTransform decryptor = AESProvider.CreateDecryptor();
  102.  
  103.             // Decrypt bytes after the IV
  104.             byte[] plainBytes = decryptor.TransformFinalBlock(secureBytes, 16, secureBytes.Length - 16);
  105.  
  106.             // Return decrypted bytes as a string
  107.             return UnicodeEncoding.Unicode.GetString(plainBytes);
  108.         }
  109.  
  110.     }
  111. }
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https://ideone.com/xQJME
language:
C# (gmcs 5.20.1)
created:
11 years ago
visibility:
public

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