private byte[] GenerateMask(byte[] seed, int outputLength)
{
if (outputLength > (Math.Pow(2, 32)))
{
throw new ArgumentException("Mask cannot exceed 2^32.");
}
else
{
var result = new List <byte>();
for (var i = 0; i <= outputLength / _rsaConfig.hLen; i++)
{
var data = new List <byte>();
data.AddRange(seed);
data.AddRange(RSAHelper.I2OSP(i, 4, false));
result.AddRange(_rsaConfig.ComputeHash(data.ToArray()));
}
if (outputLength <= result.Count)
{
return(result.GetRange(0, outputLength).ToArray());
}
else
{
throw new ArgumentException("mask length invalid.");
}
}
}
public byte[] CrunchRSA(byte[] plainText, bool usePrivate)
{
if (usePrivate && (!_rsaConfig.Has_PRIVATE_Info))
{
throw new CryptographicException("No private key");
}
if ((usePrivate == false) && (!_rsaConfig.Has_PUBLIC_Info))
{
throw new CryptographicException("No public key");
}
BigInteger e;
if (usePrivate)
{
e = _rsaConfig.D;
}
else
{
e = _rsaConfig.E;
}
var PT = RSAHelper.OS2IP(plainText, false);
var M = BigInteger.ModPow(PT, e, _rsaConfig.N);
return(M.Sign == -1 ?
RSAHelper.I2OSP(M + _rsaConfig.N, _rsaConfig.OctetsInModulus, false) :
RSAHelper.I2OSP(M, _rsaConfig.OctetsInModulus, false));
}
public byte[] PrivateDecryptFast(byte[] data)
{
if (!_rsaConfig.Has_PRIVATE_Info || !_rsaConfig.HasCRTInfo)
{
throw new CryptographicException("No private key");
}
else
{
var c = RSAHelper.OS2IP(data, false);
var m1 = BigInteger.ModPow(c, _rsaConfig.DP, _rsaConfig.P);
var m2 = BigInteger.ModPow(c, _rsaConfig.DQ, _rsaConfig.Q);
var h = ((m1 - m2) * _rsaConfig.InverseQ) % _rsaConfig.P;
var m = (m2 + (_rsaConfig.Q * h));
return(m.Sign == -1 ?
RSAHelper.I2OSP(m + _rsaConfig.N, _rsaConfig.OctetsInModulus, false)
: RSAHelper.I2OSP(m, _rsaConfig.OctetsInModulus, false));
}
}
