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/*
* GOST 34.10-2001 implemenation
* (C) 2007 Falko Strenzke, FlexSecure GmbH
* Manuel Hartl, FlexSecure GmbH
* (C) 2008-2010 Jack Lloyd
*
* Distributed under the terms of the Botan license
*/
#include <botan/gost_3410.h>
#include <botan/der_enc.h>
#include <botan/ber_dec.h>
namespace Botan {
std::vector<byte> GOST_3410_PublicKey::x509_subject_public_key() const
{
// Trust CryptoPro to come up with something obnoxious
const BigInt x = public_point().get_affine_x();
const BigInt y = public_point().get_affine_y();
size_t part_size = std::max(x.bytes(), y.bytes());
std::vector<byte> bits(2*part_size);
x.binary_encode(&bits[part_size - x.bytes()]);
y.binary_encode(&bits[2*part_size - y.bytes()]);
// Keys are stored in little endian format (WTF)
for(size_t i = 0; i != part_size / 2; ++i)
{
std::swap(bits[i], bits[part_size-1-i]);
std::swap(bits[part_size+i], bits[2*part_size-1-i]);
}
return DER_Encoder().encode(bits, OCTET_STRING).get_contents_unlocked();
}
AlgorithmIdentifier GOST_3410_PublicKey::algorithm_identifier() const
{
std::vector<byte> params =
DER_Encoder().start_cons(SEQUENCE)
.encode(OID(domain().get_oid()))
.end_cons()
.get_contents_unlocked();
return AlgorithmIdentifier(get_oid(), params);
}
GOST_3410_PublicKey::GOST_3410_PublicKey(const AlgorithmIdentifier& alg_id,
const secure_vector<byte>& key_bits)
{
OID ecc_param_id;
// Also includes hash and cipher OIDs... brilliant design guys
BER_Decoder(alg_id.parameters).start_cons(SEQUENCE).decode(ecc_param_id);
domain_params = EC_Group(ecc_param_id);
secure_vector<byte> bits;
BER_Decoder(key_bits).decode(bits, OCTET_STRING);
const size_t part_size = bits.size() / 2;
// Keys are stored in little endian format (WTF)
for(size_t i = 0; i != part_size / 2; ++i)
{
std::swap(bits[i], bits[part_size-1-i]);
std::swap(bits[part_size+i], bits[2*part_size-1-i]);
}
BigInt x(&bits[0], part_size);
BigInt y(&bits[part_size], part_size);
public_key = PointGFp(domain().get_curve(), x, y);
BOTAN_ASSERT(public_key.on_the_curve(),
"Loaded GOST 34.10 public key is on the curve");
}
namespace {
BigInt decode_le(const byte msg[], size_t msg_len)
{
secure_vector<byte> msg_le(msg, msg + msg_len);
for(size_t i = 0; i != msg_le.size() / 2; ++i)
std::swap(msg_le[i], msg_le[msg_le.size()-1-i]);
return BigInt(&msg_le[0], msg_le.size());
}
}
GOST_3410_Signature_Operation::GOST_3410_Signature_Operation(
const GOST_3410_PrivateKey& gost_3410) :
base_point(gost_3410.domain().get_base_point()),
order(gost_3410.domain().get_order()),
x(gost_3410.private_value())
{
}
secure_vector<byte>
GOST_3410_Signature_Operation::sign(const byte msg[], size_t msg_len,
RandomNumberGenerator& rng)
{
BigInt k;
do
k.randomize(rng, order.bits()-1);
while(k >= order);
BigInt e = decode_le(msg, msg_len);
e %= order;
if(e == 0)
e = 1;
PointGFp k_times_P = base_point * k;
BOTAN_ASSERT(k_times_P.on_the_curve(),
"GOST 34.10 k*g is on the curve");
BigInt r = k_times_P.get_affine_x() % order;
BigInt s = (r*x + k*e) % order;
if(r == 0 || s == 0)
throw Invalid_State("GOST 34.10: r == 0 || s == 0");
secure_vector<byte> output(2*order.bytes());
s.binary_encode(&output[output.size() / 2 - s.bytes()]);
r.binary_encode(&output[output.size() - r.bytes()]);
return output;
}
GOST_3410_Verification_Operation::GOST_3410_Verification_Operation(const GOST_3410_PublicKey& gost) :
base_point(gost.domain().get_base_point()),
public_point(gost.public_point()),
order(gost.domain().get_order())
{
}
bool GOST_3410_Verification_Operation::verify(const byte msg[], size_t msg_len,
const byte sig[], size_t sig_len)
{
if(sig_len != order.bytes()*2)
return false;
BigInt e = decode_le(msg, msg_len);
BigInt s(sig, sig_len / 2);
BigInt r(sig + sig_len / 2, sig_len / 2);
if(r <= 0 || r >= order || s <= 0 || s >= order)
return false;
e %= order;
if(e == 0)
e = 1;
BigInt v = inverse_mod(e, order);
BigInt z1 = (s*v) % order;
BigInt z2 = (-r*v) % order;
PointGFp R = multi_exponentiate(base_point, z1,
public_point, z2);
if(R.is_zero())
return false;
return (R.get_affine_x() == r);
}
}
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