/// <summary>
/// Task 2. RSA Encryption and decryption
/// </summary>
/// <param name="keys">keys</param>
/// <param name="fileName"></param>
/// <param name="keyLength">Key length</param>
private static void RsaCrypt(KeysHolder keys, string fileName, int keyLength)
{
var plainText = FileWorker.GetBinaryFile(fileName);
var encodedText = new List <short>();
var decryptedText = new List <short>();
var rsaEncoder = new RsaEncoder();
// encrypting
encodedText = Encode(keys.publicKey, keys.cypherModule, plainText, rsaEncoder, keyLength / 4, keyLength, false);
// saving encrypted message
FileWorker.CreateTextFileForBinaryNumber(encodedText, "crypted.txt");
Console.WriteLine(String.Format("Encryption has finished. Check crypted.txt"));
// decrypting
decryptedText = Encode(keys.privateKey, keys.cypherModule, encodedText, rsaEncoder, keyLength, keyLength / 4, true);
// saving decrypted message
FileWorker.GetNEWFile(decryptedText, "decrypted_" + fileName);
Console.WriteLine(String.Format("DEcryption has finished. Check decrypted{0}", fileName));
Console.WriteLine("-------------------------------------------------------------");
}
/// <summary>
/// RSA Encryption and decryption. Initial message will be separated on blocks with length toTakeLength
/// Encrypted (decrypted message) are written as blocks with length toPutLength
/// </summary>
/// <param name="key">key (either public or private)</param>
/// <param name="cypherModule">cypher module</param>
/// <param name="text">message</param>
/// <param name="rsaEncoder">RSA instance</param>
/// <param name="toTakeLength"></param>
/// <param name="toPutLength"></param>
/// <returns>binary number placed in list int</returns>
private static List <short> Encode(BigInteger key, BigInteger cypherModule, List <short> text, RsaEncoder rsaEncoder, int toTakeLength, int toPutLength, bool isDecryption)
{
var toReturn = new List <short>();
while (text.Count != 0)
{
// separate message on blocks
var oneBlock = text.Take(toTakeLength);
var oneBlockNumeric = MathHelper.GetNumberFromList(oneBlock.ToList());
// encrypt(decrypt) one block
var encodedNumber = rsaEncoder.Encode(oneBlockNumeric, key, cypherModule);
var encodedBlockBinary = MathHelper.GetBinaryFromNumber(encodedNumber);
if (encodedBlockBinary[0] == 0)
{
encodedBlockBinary.RemoveAt(0); // delete first bit responsible for number sign
}
// in case decryption there is no need to fill last block with insignificant zeros
if (!(isDecryption && text.Count == toTakeLength))
{
encodedBlockBinary = Helper.BringingToNeededBinaryFormat(encodedBlockBinary, toPutLength);
}
toReturn.AddRange(encodedBlockBinary);
// remove block which has already been en(-de)crypted
text.RemoveRange(0, oneBlock.Count());
}
return(toReturn);
}
