January 26, 2011

Encrypt Decrypt password using asp dot net


 using System;  
 using System.Collections.Generic;  
 using System.Text;  
 using System.IO;  
 using System.Security.Cryptography;  
 namespace xyz  
 {  
   class abc  
   {  
     public static string Encrypt(string plainText, string passPhrase, string saltValue, string hashAlgorithm, int passwordIterations, string initVector, int keySize)  
     {  
 // Convert strings into byte arrays.  
 // Let us assume that strings only contain ASCII codes.  
 // If strings include Unicode characters, use Unicode, UTF7, or UTF8  
 // encoding.  
 byte[] initVectorBytes = Encoding.ASCII.GetBytes(initVector);  
 byte[] saltValueBytes = Encoding.ASCII.GetBytes(saltValue);  
 // Convert our plaintext into a byte array.  
 // Let us assume that plaintext contains UTF8-encoded characters.  
 byte[] plainTextBytes = Encoding.UTF8.GetBytes(plainText);  
 // First, we must create a password, from which the key will be derived.  
 // This password will be generated from the specified passphrase and  
 // salt value. The password will be created using the specified hash  
 // algorithm. Password creation can be done in several iterations.  
 PasswordDeriveBytes password = new PasswordDeriveBytes(  
    passPhrase,  
    saltValueBytes,  
    hashAlgorithm,  
    passwordIterations);  
 // Use the password to generate pseudo-random bytes for the encryption  
 // key. Specify the size of the key in bytes (instead of bits).  
 byte[] keyBytes = password.GetBytes(keySize / 8);  
 // Create uninitialized Rijndael encryption object.  
 RijndaelManaged symmetricKey = new RijndaelManaged();  
 // It is reasonable to set encryption mode to Cipher Block Chaining  
 // (CBC). Use default options for other symmetric key parameters.  
 symmetricKey.Mode = CipherMode.CBC;  
 // Generate encryptor from the existing key bytes and initialization  
 // vector. Key size will be defined based on the number of the key  
 // bytes.  
 ICryptoTransform encryptor = symmetricKey.CreateEncryptor(keyBytes, initVectorBytes);  
 // Define memory stream which will be used to hold encrypted data.  
 MemoryStream memoryStream = new MemoryStream();  
 // Define cryptographic stream (always use Write mode for encryption).  
 CryptoStream cryptoStream = new CryptoStream(memoryStream,  
  encryptor,  
  CryptoStreamMode.Write);  
 // Start encrypting.  
 cryptoStream.Write(plainTextBytes, 0, plainTextBytes.Length);  
 // Finish encrypting.  
 cryptoStream.FlushFinalBlock();  
 // Convert our encrypted data from a memory stream into a byte array.  
 byte[] cipherTextBytes = memoryStream.ToArray();  
 // Close both streams.  
 memoryStream.Close();  
 cryptoStream.Close();  
 // Convert encrypted data into a base64-encoded string.  
 string cipherText = Convert.ToBase64String(cipherTextBytes);  
 // Return encrypted string.  
 return cipherText;  
     }  
     public static string Decrypt(string cipherText, string passPhrase, string saltValue,string hashAlgorithm, int passwordIterations,string initVector, int keySize)  
     {  
 // Convert strings defining encryption key characteristics into byte  
 // arrays. Let us assume that strings only contain ASCII codes.  
 // If strings include Unicode characters, use Unicode, UTF7, or UTF8  
 // encoding.  
 byte[] initVectorBytes = Encoding.ASCII.GetBytes(initVector);  
 byte[] saltValueBytes = Encoding.ASCII.GetBytes(saltValue);  
 // Convert our ciphertext into a byte array.  
 byte[] cipherTextBytes = Convert.FromBase64String(cipherText);  
 // First, we must create a password, from which the key will be  
 // derived. This password will be generated from the specified  
 // passphrase and salt value. The password will be created using  
 // the specified hash algorithm. Password creation can be done in  
 // several iterations.  
 PasswordDeriveBytes password = new PasswordDeriveBytes( passPhrase,   saltValueBytes,  
    hashAlgorithm,   passwordIterations);  
 // Use the password to generate pseudo-random bytes for the encryption  
 // key. Specify the size of the key in bytes (instead of bits).  
 byte[] keyBytes = password.GetBytes(keySize / 8);  
 // Create uninitialized Rijndael encryption object.  
 RijndaelManaged symmetricKey = new RijndaelManaged();  
 // It is reasonable to set encryption mode to Cipher Block Chaining  
 // (CBC). Use default options for other symmetric key parameters.  
 symmetricKey.Mode = CipherMode.CBC;  
 // Generate decryptor from the existing key bytes and initialization  
 // vector. Key size will be defined based on the number of the key  
 // bytes.  
 ICryptoTransform decryptor = symmetricKey.CreateDecryptor( keyBytes, initVectorBytes);  
 // Define memory stream which will be used to hold encrypted data.  
 MemoryStream memoryStream = new MemoryStream(cipherTextBytes);  
 // Define cryptographic stream (always use Read mode for encryption).  
 CryptoStream cryptoStream = new CryptoStream(memoryStream,  
   decryptor,  
   CryptoStreamMode.Read);  
 // Since at this point we don't know what the size of decrypted data  
 // will be, allocate the buffer long enough to hold ciphertext;  
 // plaintext is never longer than ciphertext.  
 byte[] plainTextBytes = new byte[cipherTextBytes.Length];  
 // Start decrypting.  
 int decryptedByteCount = cryptoStream.Read(plainTextBytes,  0, plainTextBytes.Length);  
 // Close both streams.  
 memoryStream.Close();  
 cryptoStream.Close();  
 // Convert decrypted data into a string.  
 // Let us assume that the original plaintext string was UTF8-encoded.  
 string plainText = Encoding.UTF8.GetString(plainTextBytes, 0, decryptedByteCount);  
 // Return decrypted string.   
 return plainText;  
     }  
   }  
 }