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/*
* RSA
* (C) 1999-2010 Jack Lloyd
*
* Distributed under the terms of the Botan license
*/
#include <botan/rsa.h>
#include <botan/libstate.h>
#include <botan/parsing.h>
#include <botan/numthry.h>
#include <botan/keypair.h>
#include <botan/internal/assert.h>
namespace Botan {
/*
* Create a RSA private key
*/
RSA_PrivateKey::RSA_PrivateKey(RandomNumberGenerator& rng,
u32bit bits, u32bit exp)
{
if(bits < 512)
throw Invalid_Argument(algo_name() + ": Can't make a key that is only " +
to_string(bits) + " bits long");
if(exp < 3 || exp % 2 == 0)
throw Invalid_Argument(algo_name() + ": Invalid encryption exponent");
e = exp;
do
{
p = random_prime(rng, (bits + 1) / 2, e);
q = random_prime(rng, bits - p.bits(), e);
n = p * q;
} while(n.bits() != bits);
d = inverse_mod(e, lcm(p - 1, q - 1));
d1 = d % (p - 1);
d2 = d % (q - 1);
c = inverse_mod(q, p);
gen_check(rng);
}
/*
* Check Private RSA Parameters
*/
bool RSA_PrivateKey::check_key(RandomNumberGenerator& rng, bool strong) const
{
if(!IF_Scheme_PrivateKey::check_key(rng, strong))
return false;
if(!strong)
return true;
if((e * d) % lcm(p - 1, q - 1) != 1)
return false;
return KeyPair::signature_consistency_check(rng, *this, "EMSA4(SHA-1)");
}
RSA_Private_Operation::RSA_Private_Operation(const RSA_PrivateKey& rsa) :
n(rsa.get_n()),
q(rsa.get_q()),
c(rsa.get_c()),
powermod_e_n(rsa.get_e(), rsa.get_n()),
powermod_d1_p(rsa.get_d1(), rsa.get_p()),
powermod_d2_q(rsa.get_d2(), rsa.get_q()),
mod_p(rsa.get_p())
{
BigInt k(global_state().global_rng(), n.bits() - 1);
blinder = Blinder(powermod_e_n(k), inverse_mod(k, n), n);
}
BigInt RSA_Private_Operation::private_op(const BigInt& m) const
{
if(m >= n)
throw Invalid_Argument("RSA private op - input is too large");
BigInt j1 = powermod_d1_p(m);
BigInt j2 = powermod_d2_q(m);
j1 = mod_p.reduce(sub_mul(j1, j2, c));
return mul_add(j1, q, j2);
}
SecureVector<byte>
RSA_Private_Operation::sign(const byte msg[], u32bit msg_len,
RandomNumberGenerator&)
{
/* We don't check signatures against powermod_e_n here because
PK_Signer checks verification consistency for all signature
algorithms.
*/
BigInt m(msg, msg_len);
BigInt x = blinder.unblind(private_op(blinder.blind(m)));
return BigInt::encode_1363(x, n.bytes());
}
/*
* RSA Decryption Operation
*/
SecureVector<byte>
RSA_Private_Operation::decrypt(const byte msg[], u32bit msg_len)
{
BigInt m(msg, msg_len);
BigInt x = blinder.unblind(private_op(blinder.blind(m)));
BOTAN_ASSERT(m == powermod_e_n(x),
"RSA private op failed consistency check");
return BigInt::encode(x);
}
}
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