Symmetric key Encryption and Decryption

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If your Data is not secure enough then how you can keep your clients happy in respect of security to their data? In My today’s Blog I would like to explain Symmetric key Encryption and Decryption using Rijndael algorithm.

///////////////////////////////////////////////////////////////////////////////
// SAMPLE: Symmetric key encryption and decryption using Rijndael algorithm.
// THIS CODE AND INFORMATION IS PROVIDED “AS IS” WITHOUT WARRANTY OF ANY KIND,
// EITHER EXPRESSED OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE IMPLIED
// WARRANTIES OF MERCHANTABILITY AND/OR FITNESS FOR A PARTICULAR PURPOSE.
///////////////////////////////////////////////////////////////////////////////

using System;
using System.IO;
using System.Text;
using System.Security.Cryptography;

namespace UmaMahesh.Security
{
    /// 
    /// This class uses a symmetric key algorithm (Rijndael/AES) to encrypt and
    /// decrypt data. As long as encryption and decryption routines use the same
    /// parameters to generate the keys, the keys are guaranteed to be the same.
    /// The class uses static functions with duplicate code to make it easier to
    /// demonstrate encryption and decryption logic. In a real-life application,
    /// this may not be the most efficient way of handling encryption, so – as
    /// soon as you feel comfortable with it – you may want to redesign this class.
    /// 
    public static class AESAlg
    {
        static string saltValue, hashAlgorithm, initVector, passPhrase;
        static int passwordIterations, keySize;
        static AESAlg()
        {
            //string[] EncDecKeys = System.Configuration.ConfigurationManager.AppSettings["EDVal"].Split(‘;’);
            passPhrase = EncDecProp.PassPhrase;
            saltValue = EncDecProp.SaltValue;
            hashAlgorithm = EncDecProp.HashAlgorithm;
            passwordIterations = EncDecProp.PasswordIterations;
            initVector = EncDecProp.InitVector;
            keySize = EncDecProp.KeySize;
        }

        /// 
        /// Encrypts specified plaintext using Rijndael symmetric key algorithm
        /// and returns a base64-encoded result.
        /// 
        /// 
        /// Plaintext value to be encrypted.
        /// 
        /// 
        /// Passphrase from which a pseudo-random password will be derived. The
        /// derived password will be used to generate the encryption key.
        /// Passphrase can be any string. In this example we assume that this
        /// passphrase is an ASCII string.
        /// 
        /// 
        /// Salt value used along with passphrase to generate password. Salt can
        /// be any string. In this example we assume that salt is an ASCII string.
        /// 
        /// 
        /// Hash algorithm used to generate password. Allowed values are: “MD5? and
        /// “SHA1?. SHA1 hashes are a bit slower, but more secure than MD5 hashes.
        /// 
        /// 
        /// Number of iterations used to generate password. One or two iterations
        /// should be enough.
        /// 
        /// 
        /// Initialization vector (or IV). This value is required to encrypt the
        /// first block of plaintext data. For RijndaelManaged class IV must be
        /// exactly 16 ASCII characters long.
        /// 
        /// 
        /// Size of encryption key in bits. Allowed values are: 128, 192, and 256.
        /// Longer keys are more secure than shorter keys.
        /// 
        /// 
        /// Encrypted value formatted as a base64-encoded string.
        /// 

        public static string Encrypt(string plainText)
        {
            // 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;
        }

        /// 
        /// Decrypts specified ciphertext using Rijndael symmetric key algorithm.
        /// 
        /// 
        /// Base64-formatted ciphertext value.
        /// 
        /// 
        /// Passphrase from which a pseudo-random password will be derived. The
        /// derived password will be used to generate the encryption key.
        /// Passphrase can be any string. In this example we assume that this
        /// passphrase is an ASCII string.
        /// 
        /// 
        /// Salt value used along with passphrase to generate password. Salt can
        /// be any string. In this example we assume that salt is an ASCII string.
        /// 
        /// 
        /// Hash algorithm used to generate password. Allowed values are: “MD5? and
        /// “SHA1?. SHA1 hashes are a bit slower, but more secure than MD5 hashes.
        /// 
        /// 
        /// Number of iterations used to generate password. One or two iterations
        /// should be enough.
        /// 
        /// 
        /// Initialization vector (or IV). This value is required to encrypt the
        /// first block of plaintext data. For RijndaelManaged class IV must be
        /// exactly 16 ASCII characters long.
        /// 
        /// 
        /// Size of encryption key in bits. Allowed values are: 128, 192, and 256.
        /// Longer keys are more secure than shorter keys.
        /// 
        /// 
        /// Decrypted string value.
        /// 
        /// 
        /// Most of the logic in this function is similar to the Encrypt
        /// logic. In order for decryption to work, all parameters of this function
        /// – except cipherText value – must match the corresponding parameters of
        /// the Encrypt function which was called to generate the
        /// ciphertext.
        /// 
        public static string Decrypt(string cipherText)
        {
            // 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;
        }
    }
    static class EncDecProp
    {
        public static readonly string PassPhrase = "Uw@W@h3$h", HashAlgorithm = "SHA1", SaltValue = "s@lTMagi”, InitVector = “@AB2cd3EF4gh5IJ$";
        public static readonly int KeySize = 256, PasswordIterations = 2;
    }
}

PS: Please Change PassPhrase, SaltValue, InitVector Values based on your Choice. Based on those key values the Encryption and Decryption of the Data Happens

Hope You Enjoyed the blog…

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