rsa-new.cs

private static string EncryptPassword(EncryptPasswordModel encryptPasswordModel) {
	// Convert the public keys to BigIntegers
	var modulus = CreateBigInteger(encryptPasswordModel.PublicKeyMod);
	var exponent = CreateBigInteger(encryptPasswordModel.PublicKeyExp);

	// Original: $data = this.pkcs1pad2($data,($pubkey.modulus.bitLength()+7)>>3);
	// I'm going to hardcode the bitlength, I can't figure that out right now.
	var encryptedNumber = Pkcs1Pad2(encryptPasswordModel.Password, (2048 + 7) >> 3);

	// And now, the RSA encryption
	encryptedNumber = BigInteger.ModPow(encryptedNumber, exponent, modulus);

	// Finally we convert the encrypted string back to Base16
	var encryptedString = encryptedNumber.ToString("x");

	// And then we decode it back
	// And we put it back into Base64
	encryptedString = EncodeBase64(DecodeHex(encryptedString));

	return encryptedString;
}

public static string DecodeHex(string input) {
	var stringBuilder = new StringBuilder();
	var i = 0;
	do {
		var a = ((Hex.IndexOf(input[i++]) << 4) & 0xf0);
		var b = 0;

		if (i < input.Length) b = (Hex.IndexOf(input[i++]) & 0xf);

		stringBuilder.Append(new[] { (char)(a | b)
		});
	} while ( i < input . Length );

	return stringBuilder.ToString();
}

public static string EncodeBase64(string input) {
	var stringBuilder = new StringBuilder();
	var i = 0;

	do {
		var x = 0;
		int chr1 = input[i++];
		int chr2, chr3;
		if (input.Length > i) {
			chr2 = input.Length > i ? input[i++] : 0;

			if (input.Length > i) {
				chr3 = input.Length > i ? input[i++] : 0;
			}
			else {
				x = 2;
				chr3 = 0;
			}
		}
		else {
			x = 1;
			chr2 = 0;
			chr3 = 0;
		}

		var enc1 = chr1 >> 2;
		var enc2 = ((chr1 & 3) << 4) | (chr2 >> 4);
		var enc3 = ((chr2 & 15) << 2) | (chr3 >> 6);
		var enc4 = chr3 & 63;

		if (x == 1) enc3 = enc4 = 64;
		else if (x == 2) enc4 = 64;

		stringBuilder.Append(new[] {
			Base64[enc1],
			Base64[enc2],
			Base64[enc3],
			Base64[enc4]
		});
	} while ( i < input . Length );

	return stringBuilder.ToString();
}

/// <summary>
/// Encodes the data
/// </summary>
/// <param name="data"></param>
/// <param name="keySize"></param>
/// <returns></returns>
public static BigInteger Pkcs1Pad2(string data, int keySize) {
	if (keySize < data.Length + 11) return new BigInteger();

	var buffer = new byte[256];
	var i = data.Length - 1;

	while (i >= 0 && keySize > 0) {
		buffer[--keySize] = (byte) data[i--];
	}

	// Padding, I think
	var random = new Random();
	buffer[--keySize] = 0;
	while (keySize > 2) {
		buffer[--keySize] = (byte) random.Next(1, 256);
		//buffer[--keySize] = 5;
	}

	buffer[--keySize] = 2;
	buffer[--keySize] = 0;

	Array.Reverse(buffer);

	return new BigInteger(buffer);
}

public static BigInteger CreateBigInteger(string hex) {
	return BigInteger.Parse("00" + hex, NumberStyles.AllowHexSpecifier);
}