public static List <BigInt> Encode()
{
Console.Write("Enter first prime number:");
var p = new BigInt(Console.ReadLine());
Console.Write("Enter second prime number:");
var q = new BigInt(Console.ReadLine());
var module = p * q;
Console.Write($"Your module:{module}\n");
var fi = (p - new BigInt(1)) * (q - new BigInt(1));
Console.Write($"Your fi:{fi}\n");
var publicExp = CalculatePublicExponent(fi);
Console.Write($"Your public exp:{publicExp}\n");
var privateExp = CalculatePrivateExponent(publicExp, fi);
Console.Write($"Your private exponent:{privateExp}\n");
Console.Write("Enter your message:");
var message = Encoding.ASCII
.GetBytes(Console.ReadLine() ?? string.Empty)
.Select(x => (int)x)
.ToArray();
var encodedMsg = new List <BigInt>();
Console.Write($"Your encoded message:\n");
foreach (var code in message)
{
if (new BigInt(code.ToString()) > module)
{
throw new Exception("Module is too small - use bigger prime numbers");
}
var encodedLetter = BigInt.ModPow(new BigInt(code.ToString()), publicExp, module);
encodedMsg.Add(encodedLetter);
Console.Write(encodedLetter + " ");
}
Console.WriteLine();
return(encodedMsg);
}
public static string Decode()
{
Console.Write("Enter your module:");
var module = new BigInt(Console.ReadLine());
Console.Write("Enter your private exponent:");
var privateExp = new BigInt(Console.ReadLine());
Console.Write("Enter your encoded message:");
var encodedMsg = Console.ReadLine().Split(' ');
var decodedLetters = new List <int>();
foreach (var code in encodedMsg)
{
var decodedLetter = BigInt.ModPow(new BigInt(code.ToString()), privateExp, module);
decodedLetters.Add(int.Parse(decodedLetter.ToString()));
}
var decodedMsg = Encoding.ASCII.GetString(decodedLetters.Select(x => (byte)x).ToArray());
Console.WriteLine($"Decoded message:{decodedMsg}");
return(decodedMsg);
}
public void CorrectDecode(string value, string number1, string number2)
{
var p = new BigInt(number1);
var q = new BigInt(number2);
var module = p * q;
var phi = (p - new BigInt(1)) * (q - new BigInt(1));
var publicExp = RSA.CalculatePublicExponent(phi);
var privateExp = RSA.CalculatePrivateExponent(publicExp, phi);
var message = Encoding.ASCII
.GetBytes(value)
.Select(x => (int)x)
.ToArray();
var encodedMsg = new List <BigInt>();
foreach (var code in message)
{
if (new BigInt(code.ToString()) > module)
{
throw new Exception("Module is too small - use bigger prime numbers");
}
var encodedLetter = BigInt.ModPow(new BigInt(code.ToString()), publicExp, module);
encodedMsg.Add(encodedLetter);
Console.Write(encodedLetter + " ");
}
var decodedLetters = new List <int>();
foreach (var code in encodedMsg)
{
var decodedLetter = BigInt.ModPow(new BigInt(code.ToString()), privateExp, module);
decodedLetters.Add(int.Parse(decodedLetter.ToString()));
}
var decodedMsg = Encoding.ASCII.GetString(decodedLetters.Select(x => (byte)x).ToArray());
CollectionAssert.AreEqual(decodedMsg, message);
}
