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@therightstuff

therightstuff/AES.cs

Last active Apr 4, 2020
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Simple AES 256 CBC Encryption to and Decryption from Base64 encoded strings in C#
using System;
using System.Collections.Generic;
using System.IO;
using System.Security.Cryptography;
namespace MyProject.Data.Encryption
{
public class AES
{
// https://stackoverflow.com/a/18502617/2860309
/* Wanting to stay compatible with NodeJS
* http://stackoverflow.com/questions/18502375/aes256-encryption-decryption-in-both-nodejs-and-c-sharp-net/
* http://stackoverflow.com/questions/12261540/decrypting-aes256-encrypted-data-in-net-from-node-js-how-to-obtain-iv-and-key
* http://stackoverflow.com/questions/8008253/c-sharp-version-of-openssl-evp-bytestokey-method
*
* // default iv is 0000000000000000 for simple-free-encryption-tool
* var cipher = crypto.createCipheriv('aes-256-cbc', 'secret key', '0000000000000000');
* var encrypted = cipher.update("test", 'utf8', 'base64') + cipher.final('base64');
*
* // default iv is 0000000000000000 for simple-free-encryption-tool
* var decipher = crypto.createDecipheriv('aes-256-cbc', 'secret key', '0000000000000000');
* var plain = decipher.update(encrypted, 'base64', 'utf8') + decipher.final('utf8');
*/
public const string NULL_IV = "0000000000000000";
public static string Encrypt(string input, string key, string iv = NULL_IV)
{
// simple-free-encryption-tool hashes key to ensure it's of the correct length
key = MD5Hasher.Hash(key);
return Convert.ToBase64String(EncryptStringToBytes(
input,
RawBytesFromString(key),
RawBytesFromString(iv)
));
}
public static string Decrypt(string inputBase64, string key, string iv = NULL_IV)
{
// simple-free-encryption-tool hashes key to ensure it's of the correct length
key = MD5Hasher.Hash(key);
return DecryptStringFromBytes(
Convert.FromBase64String(inputBase64),
RawBytesFromString(key),
RawBytesFromString(iv)
);
}
private static byte[] RawBytesFromString(string input)
{
var ret = new List<Byte>();
foreach (char x in input)
{
var c = (byte)((ulong)x & 0xFF);
ret.Add(c);
}
return ret.ToArray();
}
static byte[] EncryptStringToBytes(string plainText, byte[] Key, byte[] IV)
{
// Check arguments.
if (plainText == null || plainText.Length <= 0)
throw new ArgumentNullException("plainText");
if (Key == null || Key.Length <= 0)
throw new ArgumentNullException("Key");
if (IV == null || IV.Length <= 0)
throw new ArgumentNullException("Key");
byte[] encrypted;
// Create an RijndaelManaged object
// with the specified key and IV.
using (RijndaelManaged cipher = new RijndaelManaged())
{
cipher.Key = Key;
cipher.IV = IV;
//cipher.Mode = CipherMode.CBC;
//cipher.Padding = PaddingMode.PKCS7;
// Create a decrytor to perform the stream transform.
ICryptoTransform encryptor = cipher.CreateEncryptor(cipher.Key, cipher.IV);
// Create the streams used for encryption.
using (MemoryStream msEncrypt = new MemoryStream())
{
using (CryptoStream csEncrypt = new CryptoStream(msEncrypt, encryptor, CryptoStreamMode.Write))
{
using (StreamWriter swEncrypt = new StreamWriter(csEncrypt))
{
//Write all data to the stream.
swEncrypt.Write(plainText);
}
encrypted = msEncrypt.ToArray();
}
}
}
// Return the encrypted bytes from the memory stream.
return encrypted;
}
static string DecryptStringFromBytes(byte[] cipherText, byte[] Key, byte[] IV)
{
// Check arguments.
if (cipherText == null || cipherText.Length <= 0)
throw new ArgumentNullException("cipherText");
if (Key == null || Key.Length <= 0)
throw new ArgumentNullException("Key");
if (IV == null || IV.Length <= 0)
throw new ArgumentNullException("Key");
// Declare the string used to hold
// the decrypted text.
string plaintext = null;
// Create an RijndaelManaged object
// with the specified key and IV.
using (var cipher = new RijndaelManaged())
{
cipher.Key = Key;
cipher.IV = IV;
//cipher.Mode = CipherMode.CBC;
//cipher.Padding = PaddingMode.PKCS7;
// Create a decrytor to perform the stream transform.
ICryptoTransform decryptor = cipher.CreateDecryptor(cipher.Key, cipher.IV);
// Create the streams used for decryption.
using (MemoryStream msDecrypt = new MemoryStream(cipherText))
{
using (CryptoStream csDecrypt = new CryptoStream(msDecrypt, decryptor, CryptoStreamMode.Read))
{
using (StreamReader srDecrypt = new StreamReader(csDecrypt))
{
// Read the decrypted bytes from the decrypting stream
// and place them in a string.
plaintext = srDecrypt.ReadToEnd();
}
}
}
}
return plaintext;
}
public static void runTests(){
Console.WriteLine("Starting AES tests");
// start with test.js, then convert to match mocha test
string plaintext = "plaintext";
string secret = "my secret";
string iva = "thisisacorrectiv";
string ivb = "notyourcorrectiv";
string invalidIv = "invalidiv";
string encrypted = AES.Encrypt(plaintext, secret);
Console.WriteLine("-----------------------");
Console.Write("Encrypted with no iv: ");
Console.WriteLine(encrypted);
string encryptedA = AES.Encrypt(plaintext, secret, iva);
Console.WriteLine("-----------------------");
Console.Write("Encrypted with iva " + iva +": ");
Console.WriteLine(encryptedA);
string encryptedB = AES.Encrypt(plaintext, secret, ivb);
Console.WriteLine("-----------------------");
Console.Write("Encrypted with ivb " + ivb +": ");
Console.WriteLine(encryptedB);
Console.WriteLine("-----------------------");
Console.Write("Decrypted correctly with no iv: ");
Console.WriteLine(AES.Decrypt(encrypted, secret));
Console.WriteLine("-----------------------");
Console.Write("Decrypted correctly with iva " + iva + ": ");
Console.WriteLine(AES.Decrypt(encryptedA, secret, iva));
Console.WriteLine("-----------------------");
Console.Write("Decrypted incorrectly with ivb " + ivb + ": ");
Console.WriteLine(AES.Decrypt(encryptedA, secret, ivb));
try {
string encryptedC = AES.Encrypt(plaintext, secret, invalidIv);
} catch (Exception e) {
Console.WriteLine("Expected error: " + e.Message);
}
Console.WriteLine("AES tests completed");
}
}
}
using System.Text;
namespace MyProject.Data.Encryption
{
public class MD5Hasher
{
// adapted from https://stackoverflow.com/a/24031467/2860309
public static string Hash(string input)
{
// Use input string to calculate MD5 hash
using (System.Security.Cryptography.MD5 md5 = System.Security.Cryptography.MD5.Create())
{
byte[] inputBytes = System.Text.Encoding.ASCII.GetBytes(input);
byte[] hashBytes = md5.ComputeHash(inputBytes);
// Convert the byte array to hexadecimal string
StringBuilder sb = new StringBuilder();
for (int i = 0; i < hashBytes.Length; i++)
{
sb.Append(hashBytes[i].ToString("X2"));
}
return sb.ToString().ToLower();
}
}
}
}
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