Encryption and Decryption of a string

string s = "Foo bar";
string s1 = Convert.ToBase64String(Encoding.Unicode.GetBytes(s));

//And back...
string s2 = Encoding.Unicode.GetString(Convert.FromBase64String(s1))

public static string Decrypt(string encryptedText)
		{
			byte[] cipherTextBytes = Convert.FromBase64String(encryptedText);
			byte[] keyBytes = new Rfc2898DeriveBytes(PasswordHash, Encoding.ASCII.GetBytes(SaltKey)).GetBytes(256 / 8);
			var symmetricKey = new RijndaelManaged() { Mode = CipherMode.CBC, Padding = PaddingMode.None };

			var decryptor = symmetricKey.CreateDecryptor(keyBytes, Encoding.ASCII.GetBytes(VIKey));
			var memoryStream = new MemoryStream(cipherTextBytes);
			var cryptoStream = new CryptoStream(memoryStream, decryptor, CryptoStreamMode.Read);
			byte[] plainTextBytes = new byte[cipherTextBytes.Length];

			int decryptedByteCount = cryptoStream.Read(plainTextBytes, 0, plainTextBytes.Length);
			memoryStream.Close();
			cryptoStream.Close();
			return Encoding.UTF8.GetString(plainTextBytes, 0, decryptedByteCount).TrimEnd("\0".ToCharArray());
		}


public static string Encrypt(string plainText)
		{
			byte[] plainTextBytes = Encoding.UTF8.GetBytes(plainText);

			byte[] keyBytes = new Rfc2898DeriveBytes(PasswordHash, Encoding.ASCII.GetBytes(SaltKey)).GetBytes(256 / 8);
			var symmetricKey = new RijndaelManaged() { Mode = CipherMode.CBC, Padding = PaddingMode.Zeros };
			var encryptor = symmetricKey.CreateEncryptor(keyBytes, Encoding.ASCII.GetBytes(VIKey));
			
			byte[] cipherTextBytes;

			using (var memoryStream = new MemoryStream())
			{
				using (var cryptoStream = new CryptoStream(memoryStream, encryptor, CryptoStreamMode.Write))
				{
					cryptoStream.Write(plainTextBytes, 0, plainTextBytes.Length);
					cryptoStream.FlushFinalBlock();
					cipherTextBytes = memoryStream.ToArray();
					cryptoStream.Close();
				}
				memoryStream.Close();
			}
			return Convert.ToBase64String(cipherTextBytes);
		}