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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/numthry.h>
#include <botan/der_enc.h>
#include <botan/ber_dec.h>
#include <botan/secmem.h>
#include <botan/point_gfp.h>
namespace Botan {
GOST_3410_PrivateKey::GOST_3410_PrivateKey(RandomNumberGenerator& rng,
const EC_Domain_Params& dom_pars)
{
domain_params = dom_pars;
generate_private_key(rng);
}
GOST_3410_PrivateKey::GOST_3410_PrivateKey(const EC_Domain_Params& dom_pars,
const BigInt& x)
{
domain_params = dom_pars;
private_key = x;
public_key = domain().get_base_point() * private_key;
try
{
public_key.check_invariants();
}
catch(Illegal_Point)
{
throw Invalid_State("GOST_3410 key generation failed");
}
}
X509_Encoder* GOST_3410_PublicKey::x509_encoder() const
{
class GOST_3410_Key_Encoder : public X509_Encoder
{
public:
AlgorithmIdentifier alg_id() const
{
return AlgorithmIdentifier(key->get_oid(),
key->domain().DER_encode(key->domain_format()));
}
MemoryVector<byte> key_bits() const
{
// Trust CryptoPro to come up with something obnoxious
const BigInt x = key->public_point().get_affine_x();
const BigInt y = key->public_point().get_affine_y();
SecureVector<byte> bits(2*std::max(x.bytes(), y.bytes()));
y.binary_encode(bits + (bits.size() / 2 - y.bytes()));
x.binary_encode(bits + (bits.size() - y.bytes()));
return DER_Encoder().encode(bits, OCTET_STRING).get_contents();
}
GOST_3410_Key_Encoder(const GOST_3410_PublicKey* k): key(k) {}
private:
const GOST_3410_PublicKey* key;
};
return new GOST_3410_Key_Encoder(this);
}
X509_Decoder* GOST_3410_PublicKey::x509_decoder()
{
class GOST_3410_Key_Decoder : public X509_Decoder
{
public:
void alg_id(const AlgorithmIdentifier& alg_id)
{
// Also includes hash and cipher OIDs... brilliant design guys
OID ecc_param_id;
BER_Decoder ber(alg_id.parameters);
ber.start_cons(SEQUENCE).decode(ecc_param_id);
key->domain_params = EC_Domain_Params(ecc_param_id);
}
void key_bits(const MemoryRegion<byte>& bits)
{
SecureVector<byte> key_bits;
BER_Decoder ber(bits);
ber.decode(key_bits, OCTET_STRING);
const u32bit part_size = key_bits.size() / 2;
BigInt y(key_bits, part_size);
BigInt x(key_bits + part_size, part_size);
const BigInt p = key->domain().get_curve().get_p();
key->public_key = PointGFp(key->domain().get_curve(), x, y);
key->X509_load_hook();
}
GOST_3410_Key_Decoder(GOST_3410_PublicKey* k): key(k) {}
private:
GOST_3410_PublicKey* key;
};
return new GOST_3410_Key_Decoder(this);
}
bool GOST_3410_PublicKey::verify(const byte msg[], u32bit msg_len,
const byte sig[], u32bit sig_len) const
{
const BigInt& n = domain().get_order();
if(sig_len != n.bytes()*2)
return false;
// NOTE: it is not checked whether the public point is set
if(domain().get_curve().get_p() == 0)
throw Internal_Error("domain parameters not set");
BigInt e(msg, msg_len);
BigInt r(sig, sig_len / 2);
BigInt s(sig + sig_len / 2, sig_len / 2);
if(r < 0 || r >= n || s < 0 || s >= n)
return false;
e %= n;
if(e == 0)
e = 1;
BigInt v = inverse_mod(e, n);
BigInt z1 = (s*v) % n;
BigInt z2 = (-r*v) % n;
PointGFp R = (z1 * domain().get_base_point() + z2 * public_point());
return (R.get_affine_x() == r);
}
GOST_3410_PublicKey::GOST_3410_PublicKey(const EC_Domain_Params& dom_par,
const PointGFp& pub_point)
{
domain_params = dom_par;
public_key = pub_point;
domain_encoding = EC_DOMPAR_ENC_EXPLICIT;
}
SecureVector<byte>
GOST_3410_PrivateKey::sign(const byte msg[],
u32bit msg_len,
RandomNumberGenerator& rng) const
{
const BigInt& n = domain().get_order();
BigInt k;
do
k.randomize(rng, n.bits()-1);
while(k >= n);
if(private_value() == 0)
throw Internal_Error("GOST_3410::sign(): no private key");
if(n == 0)
throw Internal_Error("GOST_3410::sign(): domain parameters not set");
BigInt e(msg, msg_len);
e %= n;
if(e == 0)
e = 1;
PointGFp k_times_P = domain().get_base_point() * k;
k_times_P.check_invariants();
BigInt r = k_times_P.get_affine_x() % n;
if(r == 0)
throw Internal_Error("GOST_3410::sign: r was zero");
BigInt s = (r*private_value() + k*e) % n;
SecureVector<byte> output(2*n.bytes());
r.binary_encode(output + (output.size() / 2 - r.bytes()));
s.binary_encode(output + (output.size() - s.bytes()));
return output;
}
}
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