Encryption in ASP.NET C#

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

namespace Gabs.Helpers
{
    public static class EncryptionRijndael
    {
        private const string EncryptionKey = "gabs123";

        // This constant is used to determine the keysize of the encryption algorithm in bits.
        // We divide this by 8 within the code below to get the equivalent number of bytes.
        private const int Keysize = 256;

        // This constant determines the number of iterations for the password bytes generation function.
        private const int DerivationIterations = 1000;

        public static string Encrypt(string clearText, string passPhrase = EncryptionKey)
        {
            // Salt and IV is randomly generated each time, but is preprended to encrypted cipher text
            // so that the same Salt and IV values can be used when decrypting.
            var saltStringBytes = Generate256BitsOfRandomEntropy();
            var ivStringBytes = Generate256BitsOfRandomEntropy();
            var plainTextBytes = Encoding.UTF8.GetBytes(clearText);
            using (var password = new Rfc2898DeriveBytes(passPhrase, saltStringBytes, DerivationIterations))
            {
                var keyBytes = password.GetBytes(Keysize / 8);
                using (var symmetricKey = new RijndaelManaged())
                {
                    symmetricKey.BlockSize = 256;
                    symmetricKey.Mode = CipherMode.CBC;
                    symmetricKey.Padding = PaddingMode.PKCS7;
                    using (var encryptor = symmetricKey.CreateEncryptor(keyBytes, ivStringBytes))
                    {
                        using (var memoryStream = new MemoryStream())
                        {
                            using (var cryptoStream = new CryptoStream(memoryStream, encryptor, CryptoStreamMode.Write))
                            {
                                cryptoStream.Write(plainTextBytes, 0, plainTextBytes.Length);
                                cryptoStream.FlushFinalBlock();
                                // Create the final bytes as a concatenation of the random salt bytes, the random iv bytes and the cipher bytes.
                                var cipherTextBytes = saltStringBytes;
                                cipherTextBytes = cipherTextBytes.Concat(ivStringBytes).ToArray();
                                cipherTextBytes = cipherTextBytes.Concat(memoryStream.ToArray()).ToArray();
                                memoryStream.Close();
                                cryptoStream.Close();
                                return Convert.ToBase64String(cipherTextBytes);
                            }
                        }
                    }
                }
            }
        }

        public static string Decrypt(string cipherText, string passPhrase = EncryptionKey)
        {
            // Get the complete stream of bytes that represent:
            // [32 bytes of Salt] + [32 bytes of IV] + [n bytes of CipherText]
            var cipherTextBytesWithSaltAndIv = Convert.FromBase64String(cipherText);
            // Get the saltbytes by extracting the first 32 bytes from the supplied cipherText bytes.
            var saltStringBytes = cipherTextBytesWithSaltAndIv.Take(Keysize / 8).ToArray();
            // Get the IV bytes by extracting the next 32 bytes from the supplied cipherText bytes.
            var ivStringBytes = cipherTextBytesWithSaltAndIv.Skip(Keysize / 8).Take(Keysize / 8).ToArray();
            // Get the actual cipher text bytes by removing the first 64 bytes from the cipherText string.
            var cipherTextBytes = cipherTextBytesWithSaltAndIv.Skip((Keysize / 8) * 2).Take(cipherTextBytesWithSaltAndIv.Length - ((Keysize / 8) * 2)).ToArray();

            using (var password = new Rfc2898DeriveBytes(passPhrase, saltStringBytes, DerivationIterations))
            {
                var keyBytes = password.GetBytes(Keysize / 8);
                using (var symmetricKey = new RijndaelManaged())
                {
                    symmetricKey.BlockSize = 256;
                    symmetricKey.Mode = CipherMode.CBC;
                    symmetricKey.Padding = PaddingMode.PKCS7;
                    using (var decryptor = symmetricKey.CreateDecryptor(keyBytes, ivStringBytes))
                    {
                        using (var memoryStream = new MemoryStream(cipherTextBytes))
                        {
                            using (var cryptoStream = new CryptoStream(memoryStream, decryptor, CryptoStreamMode.Read))
                            {
                                var plainTextBytes = new byte[cipherTextBytes.Length];
                                var decryptedByteCount = cryptoStream.Read(plainTextBytes, 0, plainTextBytes.Length);
                                memoryStream.Close();
                                cryptoStream.Close();
                                return Encoding.UTF8.GetString(plainTextBytes, 0, decryptedByteCount);
                            }
                        }
                    }
                }
            }
        }

        private static byte[] Generate256BitsOfRandomEntropy()
        {
            var randomBytes = new byte[32]; // 32 Bytes will give us 256 bits.
            using (var rngCsp = new RNGCryptoServiceProvider())
            {
                // Fill the array with cryptographically secure random bytes.
                rngCsp.GetBytes(randomBytes);
            }
            return randomBytes;
        }
    }

    public static class EncryptionAES
    {
        private const string EncryptionKey = "gabs123";

        public static string Encrypt(string clearText, string passPhrase = EncryptionKey)
        {
            byte[] clearBytes = Encoding.Unicode.GetBytes(clearText);
            using (Aes encryptor = Aes.Create())
            {
                Rfc2898DeriveBytes pdb = new Rfc2898DeriveBytes(passPhrase, new byte[] { 0x49, 0x76, 0x61, 0x6e, 0x20, 0x4d, 0x65, 0x64, 0x76, 0x65, 0x64, 0x65, 0x76 });
                encryptor.Key = pdb.GetBytes(32);
                encryptor.IV = pdb.GetBytes(16);
                using (MemoryStream ms = new MemoryStream())
                {
                    using (CryptoStream cs = new CryptoStream(ms, encryptor.CreateEncryptor(), CryptoStreamMode.Write))
                    {
                        cs.Write(clearBytes, 0, clearBytes.Length);
                        cs.Close();
                    }
                    clearText = Convert.ToBase64String(ms.ToArray());
                }
            }
            return clearText;
        }
        public static string Decrypt(string cipherText, string passPhrase = EncryptionKey)
        {
            cipherText = cipherText.Replace(" ", "+");
            byte[] cipherBytes = Convert.FromBase64String(cipherText);
            using (Aes encryptor = Aes.Create())
            {
                Rfc2898DeriveBytes pdb = new Rfc2898DeriveBytes(passPhrase, new byte[] { 0x49, 0x76, 0x61, 0x6e, 0x20, 0x4d, 0x65, 0x64, 0x76, 0x65, 0x64, 0x65, 0x76 });
                encryptor.Key = pdb.GetBytes(32);
                encryptor.IV = pdb.GetBytes(16);
                using (MemoryStream ms = new MemoryStream())
                {
                    using (CryptoStream cs = new CryptoStream(ms, encryptor.CreateDecryptor(), CryptoStreamMode.Write))
                    {
                        cs.Write(cipherBytes, 0, cipherBytes.Length);
                        cs.Close();
                    }
                    cipherText = Encoding.Unicode.GetString(ms.ToArray());
                }
            }
            return cipherText;
        }
    }

    public static class EncryptionForUrl
    {
        private const string EncryptionKey = "gabs1234"; // Strictly 8 characters

        private static byte[] key = { };
        private static byte[] IV = { 0x12, 0x34, 0x56, 0x78, 0x90, 0xab, 0xcd, 0xef };

        public static string Encrypt(string clearText, string passPhrase = EncryptionKey)
        {
            passPhrase = FixPassphrase(passPhrase);

            try
            {
                key = System.Text.Encoding.UTF8.GetBytes(passPhrase);
                DESCryptoServiceProvider des = new DESCryptoServiceProvider();
                byte[] inputByteArray = Encoding.UTF8.GetBytes(clearText);
                MemoryStream ms = new MemoryStream();
                CryptoStream cs = new CryptoStream(ms,
                  des.CreateEncryptor(key, IV), CryptoStreamMode.Write);
                cs.Write(inputByteArray, 0, inputByteArray.Length);
                cs.FlushFinalBlock();
                return System.Web.HttpUtility.UrlEncode(Convert.ToBase64String(ms.ToArray())); //.Replace('+', '-').Replace('/', '_'));
            }
            catch (Exception e)
            {
                return e.Message;
            }
        }

        public static string Decrypt(string cipherText, string passPhrase = EncryptionKey)
        {
            passPhrase = FixPassphrase(passPhrase);

            cipherText = System.Web.HttpUtility.UrlDecode(cipherText); //.Replace('-', '+').Replace('_', '/');
            byte[] inputByteArray = new byte[cipherText.Length + 1];
            try
            {
                key = System.Text.Encoding.UTF8.GetBytes(passPhrase);
                DESCryptoServiceProvider des = new DESCryptoServiceProvider();
                inputByteArray = Convert.FromBase64String(cipherText);
                MemoryStream ms = new MemoryStream();
                CryptoStream cs = new CryptoStream(ms,
                  des.CreateDecryptor(key, IV), CryptoStreamMode.Write);
                cs.Write(inputByteArray, 0, inputByteArray.Length);
                cs.FlushFinalBlock();
                System.Text.Encoding encoding = System.Text.Encoding.UTF8;
                return encoding.GetString(ms.ToArray());
            }
            catch (Exception e)
            {
                return e.Message;
            }
        }

        private static string FixPassphrase(string passPhrase)
        {
            if (passPhrase.Length > 8)
                passPhrase = new string(passPhrase.Take(8).ToArray());
            else if (passPhrase.Length > 0 && passPhrase.Length < 8)
                passPhrase = passPhrase + (new String('0', 8 - passPhrase.Length));
            else if (string.IsNullOrWhiteSpace(passPhrase))
                passPhrase = EncryptionKey;

            return passPhrase;
        }

    }

    public static class EncodingForBase64
    {
        public static string Encode(string plainText)
        {
            var plainTextBytes = System.Text.Encoding.UTF8.GetBytes(plainText);
            return System.Convert.ToBase64String(plainTextBytes);
        }

        public static string Decode(string base64EncodedData)
        {
            var base64EncodedBytes = System.Convert.FromBase64String(base64EncodedData);
            return System.Text.Encoding.UTF8.GetString(base64EncodedBytes);
        }
    }
}