Encryption and Decryption in ASP.Net using C#

Encryption and Decryption

Simple program for encryption and decryption (Cryptography) in ASP.Net using C# to Encrypt a string and Decrypt an Encrypted String

Namespaces

you  have to use below namespaces for encryption and decryption (Cryptography)

using System.IO;

using System.Text;

using System.Security.Cryptography;  

C# Sample Code

below is the code using Advanced Encryption Standard (AES) method

  

public int CONST_KEYSIZE = 256;     // 192,256

public int CONST_BLOCKSIZE = 256;   // 64,128,256

private string CONST_DEFAULT_SALTKEY = "oy6TAG4OdnyB4fPV4mX2h8ZF44tOINFYUv+KwKsgmRQ="; // Blank to generate random key

Encryption Method
public string[] AESEncryption(string plainString)

{

  string[] aPassword = new string[2];

  RijndaelManaged AesEncryption = new RijndaelManaged();         

  AesEncryption.KeySize = CONST_KEYSIZE;

  AesEncryption.BlockSize = CONST_BLOCKSIZE;

  AesEncryption.Mode = CipherMode.CBC;

  AesEncryption.Padding = PaddingMode.PKCS7;          

  string saltkey = GenerateStrongSALT();  // This common method to generate SALT

  string keyStr = saltkey;          

  byte[] ivArr = Convert.FromBase64String(keyStr);           

  AesEncryption.IV = ivArr;

  AesEncryption.Key = ivArr;

  // This array will contain the plain text in bytes

  byte[] plainText = ASCIIEncoding.UTF8.GetBytes(plainString);            

  ICryptoTransform crypto = AesEncryption.CreateEncryptor();           

           

  // The result of the encrypion and decryption

  byte[] cipherText = crypto.TransformFinalBlock(plainText, 0, plainText.Length);           

  aPassword[0] = saltkey;

  aPassword[1] = Convert.ToBase64String(cipherText);

  return aPassword;

}

Decryption Method

public string AESDecryption(string encryptedString, string saltkey)

{

   RijndaelManaged AesEncryption = new RijndaelManaged();

   AesEncryption.KeySize = CONST_KEYSIZE;

   AesEncryption.BlockSize = CONST_BLOCKSIZE;

   AesEncryption.Mode = CipherMode.CBC;

   AesEncryption.Padding = PaddingMode.PKCS7;

          

   string keyStr = saltkey;

   byte[] ivArr = Convert.FromBase64String(keyStr);

   AesEncryption.IV = ivArr;

   AesEncryption.Key = ivArr;

   byte[] plainText = Convert.FromBase64String(encryptedString);

   ICryptoTransform decrypto = AesEncryption.CreateDecryptor();

   byte[] decryptedText = decrypto.TransformFinalBlock(plainText, 0, plainText.Length);

   return ASCIIEncoding.UTF8.GetString(decryptedText);

   
}

Comman Method to Genereate SALT

public string GenerateStrongSALT()

{

  if (string.IsNullOrEmpty(CONST_DEFAULT_SALTKEY))

    {

      int arraysize = (CONST_BLOCKSIZE / 16);

      RNGCryptoServiceProvider objSalt = new RNGCryptoServiceProvider();

      byte[] ar = new byte[arraysize];

      objSalt.GetBytes(ar);

     string sHashWithSalt = Encoding.UTF8.GetString(ar, 0, ar.Length);

     byte[] saltedHashBytes = Encoding.UTF8.GetBytes(sHashWithSalt);

     HashAlgorithm algorithm = new SHA256Managed();

     byte[] hash = algorithm.ComputeHash(saltedHashBytes);

     return Convert.ToBase64String(hash);

   }

  else

   {

     return CONST_DEFAULT_SALTKEY;

    }
}