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/*
* GOST 34.10-2001 implemenation
* (C) 2007 Falko Strenzke, FlexSecure GmbH
* Manuel Hartl, FlexSecure GmbH
* (C) 2008-2010,2015,2018 Jack Lloyd
*
* Botan is released under the Simplified BSD License (see license.txt)
*/
#include <botan/gost_3410.h>
#include <botan/internal/pk_ops_impl.h>
#include <botan/reducer.h>
#include <botan/der_enc.h>
#include <botan/ber_dec.h>
namespace Botan {
std::vector<uint8_t> GOST_3410_PublicKey::public_key_bits() const
{
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<uint8_t> 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<uint8_t> params =
DER_Encoder().start_cons(SEQUENCE)
.encode(domain().get_curve_oid())
.end_cons()
.get_contents_unlocked();
return AlgorithmIdentifier(get_oid(), params);
}
GOST_3410_PublicKey::GOST_3410_PublicKey(const AlgorithmIdentifier& alg_id,
const std::vector<uint8_t>& key_bits)
{
OID ecc_param_id;
// The parameters also includes hash and cipher OIDs
BER_Decoder(alg_id.get_parameters()).start_cons(SEQUENCE).decode(ecc_param_id);
m_domain_params = EC_Group(ecc_param_id);
secure_vector<uint8_t> 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.data(), part_size);
BigInt y(&bits[part_size], part_size);
m_public_key = domain().point(x, y);
BOTAN_ASSERT(m_public_key.on_the_curve(),
"Loaded GOST 34.10 public key is on the curve");
}
namespace {
BigInt decode_le(const uint8_t msg[], size_t msg_len)
{
secure_vector<uint8_t> 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.data(), msg_le.size());
}
/**
* GOST-34.10 signature operation
*/
class GOST_3410_Signature_Operation final : public PK_Ops::Signature_with_EMSA
{
public:
GOST_3410_Signature_Operation(const GOST_3410_PrivateKey& gost_3410,
const std::string& emsa) :
PK_Ops::Signature_with_EMSA(emsa),
m_group(gost_3410.domain()),
m_base_point(m_group.get_base_point(), m_group.get_order()),
m_x(gost_3410.private_value())
{}
size_t max_input_bits() const override { return m_group.get_order_bits(); }
secure_vector<uint8_t> raw_sign(const uint8_t msg[], size_t msg_len,
RandomNumberGenerator& rng) override;
private:
const EC_Group m_group;
Blinded_Point_Multiply m_base_point;
const BigInt& m_x;
};
secure_vector<uint8_t>
GOST_3410_Signature_Operation::raw_sign(const uint8_t msg[], size_t msg_len,
RandomNumberGenerator& rng)
{
BigInt k;
do
{
k.randomize(rng, m_group.get_order_bits() - 1);
} while(k >= m_group.get_order());
BigInt e = decode_le(msg, msg_len);
e = m_group.mod_order(e);
if(e == 0)
e = 1;
const PointGFp k_times_P = m_base_point.blinded_multiply(k, rng);
BOTAN_ASSERT(k_times_P.on_the_curve(), "GOST 34.10 k*g is on the curve");
const BigInt r = m_group.mod_order(k_times_P.get_affine_x());
const BigInt s = m_group.mod_order(r*m_x + k*e);
if(r == 0 || s == 0)
throw Internal_Error("GOST 34.10 signature generation failed, r/s equal to zero");
return BigInt::encode_fixed_length_int_pair(s, r, m_group.get_order_bytes());
}
/**
* GOST-34.10 verification operation
*/
class GOST_3410_Verification_Operation final : public PK_Ops::Verification_with_EMSA
{
public:
GOST_3410_Verification_Operation(const GOST_3410_PublicKey& gost,
const std::string& emsa) :
PK_Ops::Verification_with_EMSA(emsa),
m_group(gost.domain()),
m_public_point(gost.public_point())
{}
size_t max_input_bits() const override { return m_group.get_order_bits(); }
bool with_recovery() const override { return false; }
bool verify(const uint8_t msg[], size_t msg_len,
const uint8_t sig[], size_t sig_len) override;
private:
const EC_Group m_group;
const PointGFp& m_public_point;
};
bool GOST_3410_Verification_Operation::verify(const uint8_t msg[], size_t msg_len,
const uint8_t sig[], size_t sig_len)
{
if(sig_len != m_group.get_order_bytes() * 2)
return false;
const BigInt s(sig, sig_len / 2);
const BigInt r(sig + sig_len / 2, sig_len / 2);
const BigInt& order = m_group.get_order();
if(r <= 0 || r >= order || s <= 0 || s >= order)
return false;
BigInt e = decode_le(msg, msg_len);
e = m_group.mod_order(e);
if(e == 0)
e = 1;
const BigInt v = inverse_mod(e, order);
const BigInt z1 = m_group.multiply_mod_order(s, v);
const BigInt z2 = m_group.multiply_mod_order(-r, v);
const PointGFp R = m_group.point_multiply(z1, m_public_point, z2);
if(R.is_zero())
return false;
return (R.get_affine_x() == r);
}
}
std::unique_ptr<PK_Ops::Verification>
GOST_3410_PublicKey::create_verification_op(const std::string& params,
const std::string& provider) const
{
if(provider == "base" || provider.empty())
return std::unique_ptr<PK_Ops::Verification>(new GOST_3410_Verification_Operation(*this, params));
throw Provider_Not_Found(algo_name(), provider);
}
std::unique_ptr<PK_Ops::Signature>
GOST_3410_PrivateKey::create_signature_op(RandomNumberGenerator& /*rng*/,
const std::string& params,
const std::string& provider) const
{
if(provider == "base" || provider.empty())
return std::unique_ptr<PK_Ops::Signature>(new GOST_3410_Signature_Operation(*this, params));
throw Provider_Not_Found(algo_name(), provider);
}
}
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