/// <summary>
/// Low level RSA Process function for use with private key.
/// Should never be used; Because without padding RSA is vulnerable to attacks. Use with caution.
/// </summary>
/// <param name="plainText">Data to encrypt. Length must be less than Modulus size in octets.</param>
/// <param name="usePrivate">True to use Private key, else Public.</param>
/// <returns>Encrypted Data</returns>
private byte[] RSAProcess(byte[] plainText, bool usePrivate)
{
if (usePrivate && !rsaParams.HasPrivateInfo)
{
throw new CryptographicException("RSA Process: Incomplete Private Key Info");
}
if (usePrivate == false && !rsaParams.HasPublicInfo)
{
throw new CryptographicException("RSA Process: Incomplete Public Key Info");
}
BigInteger e = usePrivate ? rsaParams.D : rsaParams.E;
BigInteger pt = RSAxUtils.OS2IP(plainText, false);
BigInteger m = BigInteger.ModPow(pt, e, rsaParams.N);
if (m.Sign == -1)
{
return(RSAxUtils.I2OSP(m + rsaParams.N, rsaParams.OctetsInModulus, false));
}
else
{
return(RSAxUtils.I2OSP(m, rsaParams.OctetsInModulus, false));
}
}
/// <summary>
/// Low level RSA Decryption function for use with private key. Uses CRT and is Much faster.
/// Should never be used; Because without padding RSA is vulnerable to attacks. Use with caution.
/// </summary>
/// <param name="data">Data to encrypt. Length must be less than Modulus size in octets.</param>
/// <returns>Encrypted Data</returns>
private byte[] RSADecryptPrivateCRT(byte[] data)
{
if (rsaParams.HasPrivateInfo && rsaParams.HasCRTInfo)
{
BigInteger c = RSAxUtils.OS2IP(data, false);
BigInteger m1 = BigInteger.ModPow(c, rsaParams.DP, rsaParams.P);
BigInteger m2 = BigInteger.ModPow(c, rsaParams.DQ, rsaParams.Q);
BigInteger h = (m1 - m2) * rsaParams.InverseQ % rsaParams.P;
BigInteger m = m2 + rsaParams.Q * h;
if (m.Sign == -1)
{
return(RSAxUtils.I2OSP(m + rsaParams.N, rsaParams.OctetsInModulus, false));
}
else
{
return(RSAxUtils.I2OSP(m, rsaParams.OctetsInModulus, false));
}
}
else
{
throw new CryptographicException("RSA Decrypt CRT: Incomplete Key Info");
}
}
/// <summary>
/// Mask Generation Function
/// </summary>
/// <param name="z">Initial pseudorandom Seed.</param>
/// <param name="l">Length of output required.</param>
/// <returns></returns>
private byte[] MGF(byte[] z, int l)
{
if (l > Math.Pow(2, 32))
{
throw new ArgumentException("Mask too long.");
}
List <byte> result = new List <byte>();
for (int i = 0; i <= l / rsaParams.HLen; i++)
{
List <byte> data = new List <byte>();
data.AddRange(z);
data.AddRange(RSAxUtils.I2OSP(i, 4, false));
result.AddRange(rsaParams.ComputeHash(data.ToArray()));
}
if (l > result.Count)
{
throw new ArgumentException("Invalid Mask Length.");
}
return(result.GetRange(0, l).ToArray());
}
