// Apply the private key to a value.
private byte[] ApplyPrivate(byte[] value)
{
if (rsaParams.P != null)
{
// Use the Chinese Remainder Theorem exponents.
// Based on the description in PKCS #1.
byte[] m1 = CryptoMethods.NumPow(value, rsaParams.DP,
rsaParams.P);
byte[] m2 = CryptoMethods.NumPow(value, rsaParams.DQ,
rsaParams.Q);
byte[] diff = CryptoMethods.NumSub(m1, m2, null);
byte[] h = CryptoMethods.NumMul(diff,
rsaParams.InverseQ,
rsaParams.P);
byte[] prod = CryptoMethods.NumMul(rsaParams.Q, h, null);
byte[] m = CryptoMethods.NumAdd(m2, prod, null);
// Clear all temporary values.
Array.Clear(m1, 0, m1.Length);
Array.Clear(m2, 0, m2.Length);
Array.Clear(diff, 0, diff.Length);
Array.Clear(h, 0, h.Length);
Array.Clear(prod, 0, prod.Length);
// Return the decrypted message.
return(m);
}
else if (rsaParams.D != null)
{
// Use the private exponent directly.
return(CryptoMethods.NumPow(value, rsaParams.D,
rsaParams.Modulus));
}
else
{
// Insufficient parameters for private key operations.
throw new CryptographicException
(_("Crypto_RSAParamsNotSet"));
}
}
