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/*
* SM2
* (C) 2017 Ribose Inc
*
* Botan is released under the Simplified BSD License (see license.txt)
*/
#include <botan/sm2.h>
#include <botan/internal/pk_ops_impl.h>
#include <botan/keypair.h>
#include <botan/reducer.h>
#include <botan/hash.h>
namespace Botan {
bool SM2_Signature_PrivateKey::check_key(RandomNumberGenerator& rng,
bool strong) const
{
if(!public_point().on_the_curve())
return false;
if(!strong)
return true;
return KeyPair::signature_consistency_check(rng, *this, "SM3");
}
SM2_Signature_PrivateKey::SM2_Signature_PrivateKey(const AlgorithmIdentifier& alg_id,
const secure_vector<uint8_t>& key_bits) :
EC_PrivateKey(alg_id, key_bits)
{
m_da_inv = inverse_mod(m_private_key + 1, domain().get_order());
}
SM2_Signature_PrivateKey::SM2_Signature_PrivateKey(RandomNumberGenerator& rng,
const EC_Group& domain,
const BigInt& x) :
EC_PrivateKey(rng, domain, x)
{
m_da_inv = inverse_mod(m_private_key + 1, domain.get_order());
}
namespace {
std::vector<uint8_t> compute_za(HashFunction& hash,
const std::string& user_id,
const EC_Group& domain,
const PointGFp& pubkey)
{
if(user_id.size() >= 8192)
throw Invalid_Argument("SM2 user id too long to represent");
const uint16_t uid_len = static_cast<uint16_t>(8 * user_id.size());
hash.update(get_byte(0, uid_len));
hash.update(get_byte(1, uid_len));
hash.update(user_id);
const size_t p_bytes = domain.get_curve().get_p().bytes();
hash.update(BigInt::encode_1363(domain.get_curve().get_a(), p_bytes));
hash.update(BigInt::encode_1363(domain.get_curve().get_b(), p_bytes));
hash.update(BigInt::encode_1363(domain.get_base_point().get_affine_x(), p_bytes));
hash.update(BigInt::encode_1363(domain.get_base_point().get_affine_y(), p_bytes));
hash.update(BigInt::encode_1363(pubkey.get_affine_x(), p_bytes));
hash.update(BigInt::encode_1363(pubkey.get_affine_y(), p_bytes));
std::vector<uint8_t> za(hash.output_length());
hash.final(za.data());
return za;
}
/**
* SM2 signature operation
*/
class SM2_Signature_Operation : public PK_Ops::Signature
{
public:
SM2_Signature_Operation(const SM2_Signature_PrivateKey& sm2,
const std::string& ident) :
m_order(sm2.domain().get_order()),
m_base_point(sm2.domain().get_base_point(), m_order),
m_x(sm2.private_value()),
m_da_inv(sm2.get_da_inv()),
m_mod_order(m_order),
m_hash(HashFunction::create_or_throw("SM3"))
{
// ZA=H256(ENTLA || IDA || a || b || xG || yG || xA || yA)
m_za = compute_za(*m_hash, ident, sm2.domain(), sm2.public_point());
m_hash->update(m_za);
}
void update(const uint8_t msg[], size_t msg_len) override
{
m_hash->update(msg, msg_len);
}
secure_vector<uint8_t> sign(RandomNumberGenerator& rng) override;
private:
const BigInt& m_order;
Blinded_Point_Multiply m_base_point;
const BigInt& m_x;
const BigInt& m_da_inv;
Modular_Reducer m_mod_order;
std::vector<uint8_t> m_za;
std::unique_ptr<HashFunction> m_hash;
};
secure_vector<uint8_t>
SM2_Signature_Operation::sign(RandomNumberGenerator& rng)
{
const BigInt k = BigInt::random_integer(rng, 1, m_order);
const PointGFp k_times_P = m_base_point.blinded_multiply(k, rng);
const BigInt e = BigInt::decode(m_hash->final());
const BigInt r = m_mod_order.reduce(k_times_P.get_affine_x() + e);
const BigInt s = m_mod_order.multiply(m_da_inv, (k - r*m_x));
// prepend ZA for next signature if any
m_hash->update(m_za);
return BigInt::encode_fixed_length_int_pair(r, s, m_order.bytes());
}
/**
* SM2 verification operation
*/
class SM2_Verification_Operation : public PK_Ops::Verification
{
public:
SM2_Verification_Operation(const SM2_Signature_PublicKey& sm2,
const std::string& ident) :
m_base_point(sm2.domain().get_base_point()),
m_public_point(sm2.public_point()),
m_order(sm2.domain().get_order()),
m_mod_order(m_order),
m_hash(HashFunction::create_or_throw("SM3"))
{
// ZA=H256(ENTLA || IDA || a || b || xG || yG || xA || yA)
m_za = compute_za(*m_hash, ident, sm2.domain(), sm2.public_point());
m_hash->update(m_za);
}
void update(const uint8_t msg[], size_t msg_len) override
{
m_hash->update(msg, msg_len);
}
bool is_valid_signature(const uint8_t sig[], size_t sig_len) override;
private:
const PointGFp& m_base_point;
const PointGFp& m_public_point;
const BigInt& m_order;
// FIXME: should be offered by curve
Modular_Reducer m_mod_order;
std::vector<uint8_t> m_za;
std::unique_ptr<HashFunction> m_hash;
};
bool SM2_Verification_Operation::is_valid_signature(const uint8_t sig[], size_t sig_len)
{
const BigInt e = BigInt::decode(m_hash->final());
// Update for next verification
m_hash->update(m_za);
if(sig_len != m_order.bytes()*2)
return false;
const BigInt r(sig, sig_len / 2);
const BigInt s(sig + sig_len / 2, sig_len / 2);
if(r <= 0 || r >= m_order || s <= 0 || s >= m_order)
return false;
const BigInt t = m_mod_order.reduce(r + s);
if(t == 0)
return false;
const PointGFp R = multi_exponentiate(m_base_point, s, m_public_point, t);
// ???
if(R.is_zero())
return false;
return (m_mod_order.reduce(R.get_affine_x() + e) == r);
}
}
std::unique_ptr<PK_Ops::Verification>
SM2_Signature_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 SM2_Verification_Operation(*this, params));
throw Provider_Not_Found(algo_name(), provider);
}
std::unique_ptr<PK_Ops::Signature>
SM2_Signature_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 SM2_Signature_Operation(*this, params));
throw Provider_Not_Found(algo_name(), provider);
}
}
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