public static byte[] Encrypt(RSAPublicKey pk,
byte[] buf, int off, int len)
{
byte[] n = pk.Modulus;
int modLen = n.Length;
byte[] x = DoPKCS1Padding(modLen, true, null, buf, off, len);
return(BigInt.ModPow(x, pk.Exponent, n));
}
public static bool Verify(RSAPublicKey pk,
byte[] header, byte[] headerAlt,
byte[] hash, int hashOff, int hashLen,
byte[] sig, int sigOff, int sigLen)
{
/*
* Signature must be an integer less than the modulus,
* but encoded over exactly the same size as the modulus.
*/
byte[] n = pk.Modulus;
int modLen = n.Length;
if (sigLen != modLen)
{
return(false);
}
byte[] x = new byte[modLen];
Array.Copy(sig, sigOff, x, 0, modLen);
if (BigInt.Compare(x, n) >= 0)
{
return(false);
}
/*
* Do the RSA exponentation, then verify and remove the
* "Type 1" padding (00 01 FF...FF 00 with at least
* eight bytes of value FF).
*/
x = BigInt.ModPow(x, pk.Exponent, n);
if (x.Length < 11 || x[0] != 0x00 || x[1] != 0x01)
{
return(false);
}
int k = 2;
while (k < x.Length && x[k] == 0xFF)
{
k++;
}
if (k < 10 || k == x.Length || x[k] != 0x00)
{
return(false);
}
k++;
/*
* Check that the remaining byte end with the provided
* hash value.
*/
int len = modLen - k;
if (len < hashLen)
{
return(false);
}
for (int i = 0; i < hashLen; i++)
{
if (x[modLen - hashLen + i] != hash[hashOff + i])
{
return(false);
}
}
len -= hashLen;
/*
* Header is at offset 'k', and length 'len'. Compare
* with the provided header(s).
*/
if (Eq(header, 0, header.Length, x, k, len))
{
return(true);
}
if (headerAlt != null)
{
if (Eq(headerAlt, 0, headerAlt.Length, x, k, len))
{
return(true);
}
}
return(false);
}
