/// <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>
/// 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);
}