public override byte[] EncryptValue( byte[] rgb )
{
if ( m_disposed )
throw new ObjectDisposedException("public key");
if ( !keypairGenerated )
GenerateKeyPair();
BigInteger input = new BigInteger(rgb);
BigInteger output = input.ModPow(e, n);
byte[] result = output.GetBytes();
// zeroize value
input.Clear();
output.Clear();
return result;
}
public override byte[] DecryptValue( byte[] rgb )
{
if ( m_disposed )
throw new ObjectDisposedException("private key");
// decrypt operation is used for signature
if ( !keypairGenerated )
GenerateKeyPair();
BigInteger input = new BigInteger(rgb);
BigInteger r = null;
// we use key blinding (by default) against timing attacks
if ( keyBlinding )
{
// x = (r^e * g) mod n
// *new* random number (so it's timing is also random)
r = BigInteger.GenerateRandom(n.BitCount());
input = r.ModPow(e, n) * input % n;
}
BigInteger output;
// decrypt (which uses the private key) can be
// optimized by using CRT (Chinese Remainder Theorem)
if ( isCRTpossible )
{
// m1 = c^dp mod p
BigInteger m1 = input.ModPow(dp, p);
// m2 = c^dq mod q
BigInteger m2 = input.ModPow(dq, q);
BigInteger h;
if ( m2 > m1 )
{
// thanks to benm!
h = p - ( ( m2 - m1 ) * qInv % p );
output = m2 + q * h;
}
else
{
// h = (m1 - m2) * qInv mod p
h = ( m1 - m2 ) * qInv % p;
// m = m2 + q * h;
output = m2 + q * h;
}
}
else
{
// m = c^i mod n
output = input.ModPow(d, n);
}
if ( keyBlinding )
{
// Complete blinding
// x^e / r mod n
output = output * r.ModInverse(n) % n;
r.Clear();
}
byte[] result = output.GetBytes();
// zeroize values
input.Clear();
output.Clear();
return result;
}
