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/*
* DSA
* (C) 1999-2010 Jack Lloyd
*
* Distributed under the terms of the Botan license
*/
#include <botan/dsa.h>
#include <botan/numthry.h>
#include <botan/keypair.h>
#include <botan/look_pk.h>
namespace Botan {
/*
* DSA_PublicKey Constructor
*/
DSA_PublicKey::DSA_PublicKey(const DL_Group& grp, const BigInt& y1)
{
group = grp;
y = y1;
core = DSA_Core(group, y);
}
/*
* DSA Verification Function
*/
bool DSA_PublicKey::verify(const byte msg[], u32bit msg_len,
const byte sig[], u32bit sig_len) const
{
return core.verify(msg, msg_len, sig, sig_len);
}
/*
* Create a DSA private key
*/
DSA_PrivateKey::DSA_PrivateKey(RandomNumberGenerator& rng,
const DL_Group& grp,
const BigInt& x_arg)
{
group = grp;
x = x_arg;
if(x == 0)
x = BigInt::random_integer(rng, 2, group_q() - 1);
y = power_mod(group_g(), x, group_p());
core = DSA_Core(group, y, x);
if(x_arg == 0)
gen_check(rng);
else
load_check(rng);
}
DSA_PrivateKey::DSA_PrivateKey(const AlgorithmIdentifier& alg_id,
const MemoryRegion<byte>& key_bits,
RandomNumberGenerator& rng) :
DL_Scheme_PrivateKey(alg_id, key_bits, DL_Group::ANSI_X9_57)
{
y = power_mod(group_g(), x, group_p());
core = DSA_Core(group, y, x);
load_check(rng);
}
/*
* Check Private DSA Parameters
*/
bool DSA_PrivateKey::check_key(RandomNumberGenerator& rng, bool strong) const
{
if(!DL_Scheme_PrivateKey::check_key(rng, strong) || x >= group_q())
return false;
if(!strong)
return true;
try
{
KeyPair::check_key(rng,
get_pk_signer(*this, "EMSA1(SHA-1)"),
get_pk_verifier(*this, "EMSA1(SHA-1)")
);
}
catch(Self_Test_Failure)
{
return false;
}
return true;
}
DSA_Signature_Operation::DSA_Signature_Operation(const DSA_PrivateKey& dsa) :
q(dsa.group_q()),
x(dsa.get_x()),
powermod_g_p(dsa.group_g(), dsa.group_p()),
mod_q(dsa.group_q())
{
}
SecureVector<byte> DSA_Signature_Operation::sign(const byte msg[],
u32bit msg_len,
RandomNumberGenerator& rng)
{
rng.add_entropy(msg, msg_len);
BigInt k;
do
k.randomize(rng, q.bits());
while(k >= q);
BigInt i(msg, msg_len);
BigInt r = mod_q.reduce(powermod_g_p(k));
BigInt s = mod_q.multiply(inverse_mod(k, q), mul_add(x, r, i));
if(r.is_zero() || s.is_zero())
throw Internal_Error("DSA signature gen failure: r or s was zero");
SecureVector<byte> output(2*q.bytes());
r.binary_encode(output + (output.size() / 2 - r.bytes()));
s.binary_encode(output + (output.size() - s.bytes()));
return output;
}
}
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