Replicate a C# RIjndael Encryption with phpseclib

Question

I have this C# Class (Below). The receiver uses this to encrypt/decrypt my messages. I am trying to use phpseclib to encrypt/decrypt and I cannot encrypt/decrypt successfully for the receiver. What is the correct implementation with phpseclib

using System; using System.IO; using System.Security.Cryptography; public class EncDec { public static byte[] Encrypt(byte[] clearData, byte[] Key, byte[] IV) { MemoryStream ms = new MemoryStream(); Rijndael alg = Rijndael.Create(); alg.Key = Key; alg.IV = IV; CryptoStream cs = new CryptoStream(ms, alg.CreateEncryptor(), CryptoStreamMode.Write); cs.Write(clearData, 0, clearData.Length); cs.Close(); byte[] encryptedData = ms.ToArray(); return encryptedData; } public static string Encrypt(string clearText, string Password) { byte[] clearBytes = System.Text.Encoding.Unicode.GetBytes(clearText); new byte[] {0x49, 0x76, 0x61, 0x6e, 0x20, 0x4d, 0x65, 0x64, 0x76, 0x65, 0x64, 0x65, 0x76}); byte[] encryptedData = Encrypt(clearBytes, pdb.GetBytes(32), pdb.GetBytes(16)); return Convert.ToBase64String(encryptedData); } public static byte[] Encrypt(byte[] clearData, string Password) { PasswordDeriveBytes pdb = new PasswordDeriveBytes(Password, new byte[] {0x49, 0x76, 0x61, 0x6e, 0x20, 0x4d, 0x65, 0x64, 0x76, 0x65, 0x64, 0x65, 0x76}); return Encrypt(clearData, pdb.GetBytes(32), pdb.GetBytes(16)); } public static void Encrypt(string fileIn, string fileOut, string Password) { FileStream fsIn = new FileStream(fileIn, FileMode.Open, FileAccess.Read); FileStream fsOut = new FileStream(fileOut, FileMode.OpenOrCreate, FileAccess.Write); PasswordDeriveBytes pdb = new PasswordDeriveBytes(Password, new byte[] {0x49, 0x76, 0x61, 0x6e, 0x20, 0x4d, 0x65, 0x64, 0x76, 0x65, 0x64, 0x65, 0x76}); Rijndael alg = Rijndael.Create(); alg.Key = pdb.GetBytes(32); alg.IV = pdb.GetBytes(16); CryptoStream cs = new CryptoStream(fsOut, alg.CreateEncryptor(), CryptoStreamMode.Write); int bufferLen = 4096; byte[] buffer = new byte[bufferLen]; int bytesRead; do { bytesRead = fsIn.Read(buffer, 0, bufferLen); cs.Write(buffer, 0, bytesRead); } while (bytesRead != 0); cs.Close(); fsIn.Close(); } public static byte[] Decrypt(byte[] cipherData, byte[] Key, byte[] IV) { MemoryStream ms = new MemoryStream(); Rijndael alg = Rijndael.Create(); alg.Key = Key; alg.IV = IV; CryptoStream cs = new CryptoStream(ms, alg.CreateDecryptor(), CryptoStreamMode.Write); cs.Write(cipherData, 0, cipherData.Length); cs.Close(); byte[] decryptedData = ms.ToArray(); return decryptedData; } public static string Decrypt(string cipherText, string Password) { byte[] cipherBytes = Convert.FromBase64String(cipherText); PasswordDeriveBytes pdb = new PasswordDeriveBytes(Password, new byte[] {0x49, 0x76, 0x61, 0x6e, 0x20, 0x4d, 0x65, 0x64, 0x76, 0x65, 0x64, 0x65, 0x76}); byte[] decryptedData = Decrypt(cipherBytes, pdb.GetBytes(32), pdb.GetBytes(16)); return System.Text.Encoding.Unicode.GetString(decryptedData); } public static byte[] Decrypt(byte[] cipherData, string Password) { PasswordDeriveBytes pdb = new PasswordDeriveBytes(Password, new byte[] {0x49, 0x76, 0x61, 0x6e, 0x20, 0x4d, 0x65, 0x64, 0x76, 0x65, 0x64, 0x65, 0x76}); return Decrypt(cipherData, pdb.GetBytes(32), pdb.GetBytes(16)); } public static void Decrypt(string fileIn, string fileOut, string Password) { FileStream fsIn = new FileStream(fileIn, FileMode.Open, FileAccess.Read); FileStream fsOut = new FileStream(fileOut, FileMode.OpenOrCreate, FileAccess.Write); PasswordDeriveBytes pdb = new PasswordDeriveBytes(Password, new byte[] {0x49, 0x76, 0x61, 0x6e, 0x20, 0x4d, 0x65, 0x64, 0x76, 0x65, 0x64, 0x65, 0x76}); Rijndael alg = Rijndael.Create(); alg.Key = pdb.GetBytes(32); alg.IV = pdb.GetBytes(16); CryptoStream cs = new CryptoStream(fsOut, alg.CreateDecryptor(), CryptoStreamMode.Write); int bufferLen = 4096; byte[] buffer = new byte[bufferLen]; int bytesRead; do { bytesRead = fsIn.Read(buffer, 0, bufferLen); cs.Write(buffer, 0, bytesRead); } while (bytesRead != 0); cs.Close(); // this will also close the unrelying fsOut stream fsIn.Close(); } }

This is an phpseclib example

 $rijndael = new \phpscelib\Crypt\Rijndael(); $rijndael->setKey($encryption_password); $clear_text = $rijndael->decrypt($cipher_text); $cipher_text = $rijndael->encrypt($clear_text);

It's likely you are missing the IV on the php side. Also, if you are deriving Rijndael keys from a password, make sure to use the same algorithm with the same salt. — Domi
– Domi, Commented Jun 22, 2017 at 7:58

Domi · Accepted Answer · 2017-06-22 08:38:09Z

Two (or three) critical issues:

You are not setting the IV on the php side.
You derive a key from a password in your c# code. For your php code, you don't (you are using the password as a key directly).
You encode the cipher bytes using Base64 in c#. The php library doesn't seem to do that although I could be wrong with that.

Security issues:

You are using a fixed salt for your PasswordDeriveBytes. Consider generating a cryptographically random salt and prepend that to your ciphertext. If you want to know why, there are plenty of good answers here.
Using a plaintext password/phrase directly for encryption (like in your php code) is considered insecure. Encryption keys should be random-ish. The output of a password hash algorithm is okay.

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