/// <summary>
/// Task 1,5. Generating of public and private keys.
/// </summary>
/// <param name="keyLength">Key length</param>
/// <param name="keyChange">For p and q length cnanging</param>
/// <returns>KeysHolder</returns>
private static KeysHolder GenerateKeys(int keyLength, int keyChange)
{
var generator = new PrimeNumbersGenerator();
// generating of prime numbers
var pNumeric = GeneratePrimeNumber(keyLength - keyChange, generator);
var qNumeric = GeneratePrimeNumber(keyLength + keyChange, generator);
Console.WriteLine(String.Format("Prime numbers p = {0} and q = {1} are generated.", pNumeric, qNumeric));
//// generating of composite numbers (on purpose)
//var pNumeric = GenerateNotPrimeNumber(keyLength, generator);
//var qNumeric = GenerateNotPrimeNumber(keyLength, generator);
//Console.WriteLine(String.Format("Составные числа p = {0} и q = {1} сгенерированы.", pNumeric, qNumeric));
// Calculating public exp, private exp and cypher module
var keysToReturn = CalculateKeysValues(keyLength, pNumeric, qNumeric, generator);
FileWorker.CreateNEWFile(keysToReturn.publicKey, "public.txt");
FileWorker.CreateNEWFile(keysToReturn.privateKey, "private.txt");
FileWorker.CreateNEWFile(keysToReturn.cypherModule, "cyphermodule.txt");
Console.WriteLine("The keys are generated and placed in public.txt, private.txt, cyphermodule.txt");
return(keysToReturn);
}
/// <summary>
/// Generating decimal prime number
/// </summary>
/// <param name="keyLength">Key length </param>
/// <returns>Big integer</returns>
private static BigInteger GeneratePrimeNumber(int keyLength, PrimeNumbersGenerator generator)
{
List <short> mask = MaskGenerator.GetMask(keyLength / 2);
// generating prime number
var primeNumber = generator.Generate(mask);
return(MathHelper.GetNumberFromList(primeNumber));
}
/// <summary>
/// ПУНКТ 3. Генерация составного числа (проверка работоспособности шифра RSA с составными числами вместо простых
/// </summary>
/// <param name="keyLength">Длина ключа</param>
/// <returns>Возвращает большое целое число</returns>
private static BigInteger GenerateNotPrimeNumber(int keyLength, PrimeNumbersGenerator generator)
{
// Подготаваливаем затравку для последующей генерации в ней простого числа.
List <short> zatravkaMaska = MaskGenerator.GetMask(keyLength / 2);
// простое число
var primeNumber = generator.GenerateNotPrime(zatravkaMaska);
return(MathHelper.GetNumberFromList(primeNumber));
}
/// <summary>
/// Getting public exp by phi and depending on key length
/// </summary>Euler function</param>
/// <param name="keyLength">Key length</param>
/// <returns>Big integer</returns>
public BigInteger GetPublicExp(BigInteger phi, int keyLength, PrimeNumbersGenerator generator)
{
int eLength = keyLength / 3; // e length
var e = MaskGenerator.GetMask(eLength);
BigInteger eNumeric = MathHelper.GetNumberFromList(e);;
var isValid = false; // is number e valid?
// Check if GCD(e, phi) equals one. If so, we found public exp
isValid = MathHelper.EvklidAlgorithm(eNumeric, phi) == 1 ? true : false;
//If number e in binary format has one in most fignificant bit and one in low bit and it is not valid then generate prime number
while (!isValid)
{
e = generator.Generate(e);
eNumeric = MathHelper.GetNumberFromList(e);
// Check if GCD(e, phi) equals one. If so, we found public exp
isValid = MathHelper.EvklidAlgorithm(eNumeric, phi) == 1 ? true : false;
}
return(eNumeric);
}
/// <summary>
/// Calculating public exp, private exp and cypher module
/// </summary>
/// <param name="keyLength">Key length</param>
/// <param name="pNumeric">First decimal prime number</param>
/// <param name="qNumeric">Second decimal prime number</param>
/// <param name="generator">prime numbers generator</param>
/// <returns>Возвращает структуру, хранящую ключи и модуль</returns>
private static KeysHolder CalculateKeysValues(int keyLength, BigInteger pNumeric, BigInteger qNumeric, PrimeNumbersGenerator generator)
{
var keysToReturn = new KeysHolder();
// Cypher module
var N = pNumeric * qNumeric;
keysToReturn.cypherModule = N;
// Euler function
var phi = (pNumeric - 1) * (qNumeric - 1);
var exponentHelper = new ExponentHelper();
// public exp
var e = exponentHelper.GetPublicExp(phi, keyLength, generator);
keysToReturn.publicKey = e;
// private exp
var d = exponentHelper.GetPrivateExp(e, phi);
keysToReturn.privateKey = d;
return(keysToReturn);
}
