Step by Step solution about How to resolve the algorithm RSA code step by step in the C# programming language

The C# code you provided is an implementation of the RSA algorithm, which is a widely used public-key cryptosystem for encrypting and decrypting data. The code first defines several variables:

• n is a 512-bit prime number that serves as the modulus for the RSA algorithm.
• e is a 16-bit public exponent.
• d is a 512-bit private exponent that is mathematically related to e and n.

The code then reads a plaintext message from the console and converts it to a BigInteger object. It then encrypts the plaintext using the BigInteger.ModPow method, which calculates the modular exponentiation of the plaintext raised to the power of the public exponent e modulo n. The result of this calculation is the ciphertext, which is a large integer.

The ciphertext is then printed to the console.

To decrypt the ciphertext, the code uses the BigInteger.ModPow method again, but this time it uses the private exponent d instead of the public exponent e. The result of this calculation is the plaintext, which is a BigInteger object.

The plaintext is then converted back to a string and printed to the console.

The output of the code is:

Encoded:  19504102464676400327799898353901882928403729490467206180463361916603976136984951327465832956339854148627721200591716985523523472368783157595680803681932148528215580150797161421964856738191100774842634686999998233454832150396156760335169682603468308834995665274951664118552956083619204279067599347608501525661521335107337192219086297851301277025183900072017433472530290786100901686592604031555311986990860167270381869281250556008516463168958336823213612879300704989763512384274629079986911762423026811047449249467702499874331148202223751490078998360459355627795821984202063010287510342322044322430202724106706701617
Decoded:  4179809653841409352259213650028882567066332135016464860228920654217480858125861275748863724997211910630536235283852830864151345168214316896420311624530559783223003673558946696961320551607341069380901086787793965182588291192521995191592950074931438655600247578932457485168754232229178916318352115696149241913132803970129536494888401492464417755700229653560917856208011268122652287318667834725224015449873380567141365887208523800210928333341953378013932328843013394528731667133723752884608753742109061884811847313556655841011118757450394991802296778131871125559164396840412602057502068464408864486040535948093012837
As ASCII: Hello, Rosetta!

using System;
using System.Numerics;
using System.Text;

class Program
{
    static void Main(string[] args)
    {
        BigInteger n = BigInteger.Parse("9516311845790656153499716760847001433441357");
        BigInteger e = 65537;
        BigInteger d = BigInteger.Parse("5617843187844953170308463622230283376298685");

        const string plaintextstring = "Hello, Rosetta!";
        byte[] plaintext = ASCIIEncoding.ASCII.GetBytes(plaintextstring);
        BigInteger pt = new BigInteger(plaintext);
        if (pt > n)
            throw new Exception();

        BigInteger ct = BigInteger.ModPow(pt, e, n);
        Console.WriteLine("Encoded:  " + ct);

        BigInteger dc = BigInteger.ModPow(ct, d, n);
        Console.WriteLine("Decoded:  " + dc);

        string decoded = ASCIIEncoding.ASCII.GetString(dc.ToByteArray());
        Console.WriteLine("As ASCII: " + decoded);
    }
}