public static byte[] Sign(RSAPrivateKey sk, byte[] header,
byte[] hash, int hashOff, int hashLen)
{
byte[] sig = new byte[sk.N.Length];
Sign(sk, header, hash, hashOff, hashLen, sig, 0);
return(sig);
}
public static byte[] Decrypt(RSAPrivateKey sk,
byte[] buf, int off, int len)
{
byte[] tmp = new byte[sk.N.Length];
int outLen = Decrypt(sk, buf, off, len, tmp, 0);
byte[] outBuf = new byte[outLen];
Array.Copy(tmp, 0, outBuf, 0, outLen);
return(outBuf);
}
public static int Sign(RSAPrivateKey sk, byte[] header,
byte[] hash, int hashOff, int hashLen,
byte[] outBuf, int outOff)
{
int modLen = sk.N.Length;
byte[] x = DoPKCS1Padding(modLen, false,
header, hash, hashOff, hashLen);
DoPrivate(sk, x);
Array.Copy(x, 0, outBuf, outOff, x.Length);
return(x.Length);
}
public static int Decrypt(RSAPrivateKey sk,
byte[] buf, int off, int len, byte[] outBuf, int outOff)
{
if (len != sk.N.Length)
{
throw new CryptoException(
"Invalid RSA-encrypted message length");
}
/*
* Note: since RSAPrivateKey refuses a modulus of less
* than 64 bytes, we know that len >= 64 here.
*/
byte[] x = new byte[len];
Array.Copy(buf, off, x, 0, len);
DoPrivate(sk, x);
if (x[0] != 0x00 || x[1] != 0x02)
{
throw new CryptoException(
"Invalid PKCS#1 v1.5 encryption padding");
}
int i;
for (i = 2; i < len && x[i] != 0x00; i++)
{
;
}
if (i < 10 || i >= len)
{
throw new CryptoException(
"Invalid PKCS#1 v1.5 encryption padding");
}
i++;
int olen = len - i;
Array.Copy(x, i, outBuf, outOff, olen);
return(olen);
}
/*
* Perform a RSA decryption. A PKCS#1 v1.5 "type 2" padding is
* expected, and removed. An exception is thrown on any error.
*
* WARNING: potentially vulnerable to Bleichenbacher's attack.
* Use with care.
*
* There are four methods, depending on input and output
* operands.
*/
public static byte[] Decrypt(RSAPrivateKey sk, byte[] buf)
{
return(Decrypt(sk, buf, 0, buf.Length));
}
public static int Sign(RSAPrivateKey sk, byte[] header,
byte[] hash, byte[] outBuf, int outOff)
{
return(Sign(sk, header, hash, 0, hash.Length, outBuf, outOff));
}
/*
* Compute a RSA signature (PKCS#1 v1.5 "type 1" padding).
* The digest header and the hashed data are provided. The
* header should be one of the standard PKCS#1 header; it
* may also be an empty array or null for a "ND" signature
* (this is normally used only in SSL/TLS up to TLS-1.1).
*/
public static byte[] Sign(RSAPrivateKey sk, byte[] header,
byte[] hash)
{
return(Sign(sk, header, hash, 0, hash.Length));
}
public static void DoPrivate(RSAPrivateKey sk,
byte[] x, int off, int len)
{
/*
* Check that the source array has the proper length
* (identical to the length of the modulus).
*/
if (len != sk.N.Length)
{
throw new CryptoException(
"Invalid source length for RSA private");
}
/*
* Reduce the source value to the proper range.
*/
ModInt mx = new ModInt(sk.N);
mx.DecodeReduce(x, off, len);
/*
* Compute m1 = x^dp mod p.
*/
ModInt m1 = new ModInt(sk.P);
m1.Set(mx);
m1.Pow(sk.DP);
/*
* Compute m2 = x^dq mod q.
*/
ModInt m2 = new ModInt(sk.Q);
m2.Set(mx);
m2.Pow(sk.DQ);
/*
* Compute h = (m1 - m2) / q mod p.
* (Result goes in m1.)
*/
ModInt m3 = m1.Dup();
m3.Set(m2);
m1.Sub(m3);
m3.Decode(sk.IQ);
m1.ToMonty();
m1.MontyMul(m3);
/*
* Compute m_2 + q*h. This works on plain integers, but
* we have efficient and constant-time code for modular
* integers, so we will do it modulo n.
*/
m3 = mx;
m3.Set(m1);
m1 = m3.Dup();
m1.Decode(sk.Q);
m1.ToMonty();
m3.MontyMul(m1);
m1.Set(m2);
m3.Add(m1);
/*
* Write result back in x[].
*/
m3.Encode(x, off, len);
}
/*
* Perform a RSA private key operation (modular exponentiation
* with the private exponent). The source array MUST have the
* same length as the modulus, and it is modified "in place".
*
* This function is constant-time, except if the source x[] does
* not have the proper length (it should be identical to the
* modulus length). If the source array has the proper length
* but the numerical value is not in the proper range, then it
* is first reduced modulo N.
*/
public static void DoPrivate(RSAPrivateKey sk, byte[] x)
{
DoPrivate(sk, x, 0, x.Length);
}
public static int Decrypt(RSAPrivateKey sk,
byte[] buf, byte[] outBuf, int outOff)
{
return(Decrypt(sk, buf, 0, buf.Length, outBuf, outOff));
}