private static byte[] OpenSSHPassphraseToKey(SecureString passphrase, byte[] iv, int length) { const int HASH_SIZE = 16; const int SALT_SIZE = 8; var md5 = new MD5CryptoServiceProvider(); //var pp = Encoding.UTF8.GetBytes(passphrase); var buf = new byte[((length + HASH_SIZE - 1) / HASH_SIZE) * HASH_SIZE]; var offset = 0; while (offset < length) { if (offset > 0) md5.TransformBlock(buf, 0, offset, null, 0); //md5.TransformBlock(pp, 0, pp.Length, null, 0); md5.HashBlock(passphrase, false); md5.TransformFinalBlock(iv, 0, SALT_SIZE); Buffer.BlockCopy(md5.Hash, 0, buf, offset, HASH_SIZE); offset += HASH_SIZE; md5.Initialize(); } md5.Clear(); var key = new byte[length]; Buffer.BlockCopy(buf, 0, key, 0, length); return key; }