The following code is based on that found in this article:
Cryptography Simplified in Microsoft .NET
The Key and the IV are needed to decrypt the encrypted text
using System;
using System.Text;
using System.Security.Cryptography;
using System.IO;
using System.Diagnostics;
...
// Simple Symmetric Encryption helper class
// Encrypts/Decrypts strings
public class SymmetricEncryptor
{
// Private Variables for this Form
private SymmetricAlgorithm m_EncryptionAlgorithmn;
//Default constructor. Default Encryption algorithmn
// to TripleDESCryptoServiceProvider
public SymmetricEncryptor()
{
m_EncryptionAlgorithmn = Rijndael.Create();
}
public SymmetricEncryptor(SymmetricAlgorithm symmetricAlgorithm)
{
m_EncryptionAlgorithmn = symmetricAlgorithm;
}
// Generate a Key for use with the Encryptor
public string GenerateKeyString()
{
m_EncryptionAlgorithmn.GenerateKey();
return Convert.ToBase64String(m_EncryptionAlgorithmn.Key);
}
// Generate an Initialisation Vector (as a string) for use with the Encryptor
public string GenerateIVString()
{
m_EncryptionAlgorithmn.GenerateIV();
return Convert.ToBase64String(m_EncryptionAlgorithmn.IV);
}
// Generate an Initialisation Vector for use with the Encryptor
public byte[] GenerateIV()
{
m_EncryptionAlgorithmn.GenerateIV();
return m_EncryptionAlgorithmn.IV;
}
// Get/Set the a Key for use with the Encryptor.
// Note the Key is provided as a Base 64 encoded string
public string KeyString
{
get
{ return Convert.ToBase64String(m_EncryptionAlgorithmn.Key); }
set
{ m_EncryptionAlgorithmn.Key = Convert.FromBase64String(value); }
}
// Get/Set the a Initialisation Vector for use
// with the Encryptor. Note the Initialisation
// Vector is provided as a Base 64 encoded string
public string IVString
{
get
{
return Convert.ToBase64String(m_EncryptionAlgorithmn.IV);
}
set
{ m_EncryptionAlgorithmn.IV = Convert.FromBase64String(value); }
}
// Get/Set the a Key for use with the Encryptor.
// Note the Key is provided as a Base 64 encoded string
public byte[] Key
{
get
{ return m_EncryptionAlgorithmn.Key; }
set
{ m_EncryptionAlgorithmn.Key = value; }
}
// Get/Set the a Initialisation Vector for use with the Encryptor.
public byte[] IV
{
get
{ return m_EncryptionAlgorithmn.IV; }
set
{ m_EncryptionAlgorithmn.IV = value; }
}
// Encrypt a string
public string EncryptToString(string Value)
{
ICryptoTransform ct = m_EncryptionAlgorithmn.CreateEncryptor(
m_EncryptionAlgorithmn.Key,
m_EncryptionAlgorithmn.IV);
byte[] bytes = Encoding.UTF8.GetBytes(Value);
bytes = ApplyCryptoTransform(bytes, ct);
return Convert.ToBase64String(bytes);
}
// Decrypt a string
public string DecryptFromString(string Value)
{
ICryptoTransform ct = m_EncryptionAlgorithmn.CreateDecryptor(
m_EncryptionAlgorithmn.Key,
m_EncryptionAlgorithmn.IV);
byte[] bytes = Convert.FromBase64String(Value);
bytes = ApplyCryptoTransform(bytes, ct);
return Encoding.UTF8.GetString(bytes);
}
// Encrypt a string
public byte[] EncryptToBytes(string Value)
{
ICryptoTransform ct = m_EncryptionAlgorithmn.CreateEncryptor(
m_EncryptionAlgorithmn.Key,
m_EncryptionAlgorithmn.IV);
byte[] bytes = Encoding.UTF8.GetBytes(Value);
bytes = ApplyCryptoTransform(bytes, ct);
return bytes;
}
// Decrypt a string
public string DecryptFromBytes(byte[] encrBytes)
{
ICryptoTransform ct = m_EncryptionAlgorithmn.CreateDecryptor(
m_EncryptionAlgorithmn.Key,
m_EncryptionAlgorithmn.IV);
byte[] bytes = ApplyCryptoTransform(encrBytes, ct);
return Encoding.UTF8.GetString(bytes);
}
private static byte[] ApplyCryptoTransform(byte[] bytes,
ICryptoTransform ct)
{
MemoryStream ms = new MemoryStream();
CryptoStream cs = new CryptoStream(ms, ct, CryptoStreamMode.Write);
cs.Write(bytes, 0, bytes.Length);
cs.FlushFinalBlock();
cs.Close();
return ms.ToArray();
}
public byte[] GenerateKey()
{
m_EncryptionAlgorithmn.GenerateKey();
return m_EncryptionAlgorithmn.Key;
}
}
Here is a tester that demonstrates usage of the class.
public class SymmetricEncryptorTester
{
public void Test()
{
string test = "98The0quick1brown2fox3jumps4over5the6lazy7cow";
byte[] key;
byte[] iv;
string encrypted;
string res;
{
SymmetricEncryptor se = new SymmetricEncryptor();
key = se.GenerateKey();
iv = se.GenerateIV();
Debug.WriteLine(ByteToArray("key", key));
Debug.WriteLine(ByteToArray("iv", iv));
encrypted = se.EncryptToString(test);
Debug.WriteLine("encrypted=" + encrypted);
}
{
SymmetricEncryptor se = new SymmetricEncryptor();
se.IV = iv;
se.Key = key;
res = se.DecryptFromString(encrypted);
Debug.Assert(res.Equals(test, StringComparison.InvariantCulture));
Debug.WriteLine("res=" + res);
}
}
public void Test2()
{
string test = "98The0quick1brown2fox3jumps4over5the6lazy7cow";
byte[] key;
byte[] iv;
byte[] encrypted;
string res = "";
{
SymmetricEncryptor se = new SymmetricEncryptor();
key = se.GenerateKey();
iv = se.GenerateIV();
Debug.WriteLine(ByteToArray("key", key));
Debug.WriteLine(ByteToArray("iv", iv));
encrypted = se.EncryptToBytes(test);
Debug.WriteLine(ByteToArray("encrypted", encrypted));
}
{
SymmetricEncryptor se = new SymmetricEncryptor();
se.IV = iv;
se.Key = key;
res = se.DecryptFromBytes(encrypted);
Debug.Assert(res.Equals(test, StringComparison.InvariantCulture));
Debug.WriteLine("res=" + res);
}
}
private string ByteToArray(string name, byte[] bytes)
{
string res = "byte[] " + name + " = new byte["
+ bytes.Length.ToString() + "] { ";
for (int ix = 0; ix < bytes.Length; ix++)
{
res += "0x" + bytes[ix].ToString("X");
if (ix < (bytes.Length - 1))
res += ", ";
}
res += " }";
return res;
}
}
