cmce.cpp

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/*
 * Classic McEliece Key Generation
 * (C) 2023 Jack Lloyd
 *     2023,2024 Fabian Albert, Amos Treiber - Rohde & Schwarz Cybersecurity
 *
 * Botan is released under the Simplified BSD License (see license.txt)
 **/
 
#include <botan/cmce.h>
#include <botan/pk_ops.h>
#include <botan/rng.h>
#include <botan/internal/cmce_decaps.h>
#include <botan/internal/cmce_encaps.h>
#include <botan/internal/cmce_keys_internal.h>
#include <botan/internal/cmce_matrix.h>
#include <botan/internal/ct_utils.h>
 
namespace Botan {
 
Classic_McEliece_PublicKey::Classic_McEliece_PublicKey(const AlgorithmIdentifier& alg_id,
                                                       std::span<const uint8_t> key_bits) :
      Classic_McEliece_PublicKey(key_bits, Classic_McEliece_Parameter_Set::from_oid(alg_id.oid())) {
   // The parameter set is identified by the OID; no parameters are defined.
   if(!alg_id.parameters_are_empty()) {
      throw Decoding_Error("Unexpected parameters for Classic McEliece public key");
   }
}
 
Classic_McEliece_PublicKey::Classic_McEliece_PublicKey(std::span<const uint8_t> key_bits,
                                                       Classic_McEliece_Parameter_Set param_set) {
   auto params = Classic_McEliece_Parameters::create(param_set);
   BOTAN_ARG_CHECK(key_bits.size() == params.pk_size_bytes(), "Wrong public key length");
   m_public = std::make_shared<Classic_McEliece_PublicKeyInternal>(
      params, Classic_McEliece_Matrix(params, {key_bits.begin(), key_bits.end()}));
}
 
Classic_McEliece_PublicKey::Classic_McEliece_PublicKey(const Classic_McEliece_PublicKey& other) {
   m_public = std::make_shared<Classic_McEliece_PublicKeyInternal>(*other.m_public);
}
 
Classic_McEliece_PublicKey& Classic_McEliece_PublicKey::operator=(const Classic_McEliece_PublicKey& other) {
   if(this != &other) {
      m_public = std::make_shared<Classic_McEliece_PublicKeyInternal>(*other.m_public);
   }
   return *this;
}
 
AlgorithmIdentifier Classic_McEliece_PublicKey::algorithm_identifier() const {
   return AlgorithmIdentifier(object_identifier(), AlgorithmIdentifier::USE_EMPTY_PARAM);
}
 
OID Classic_McEliece_PublicKey::object_identifier() const {
   return m_public->params().object_identifier();
}
 
size_t Classic_McEliece_PublicKey::key_length() const {
   // The key length is the dimension k of the goppa code (i.e. the code has 2^k codewords)
   return m_public->params().pk_no_cols();
}
 
size_t Classic_McEliece_PublicKey::estimated_strength() const {
   return m_public->params().estimated_strength();
}
 
std::vector<uint8_t> Classic_McEliece_PublicKey::public_key_bits() const {
   return raw_public_key_bits();
}
 
std::vector<uint8_t> Classic_McEliece_PublicKey::raw_public_key_bits() const {
   return m_public->matrix().bytes();
}
 
bool Classic_McEliece_PublicKey::check_key(RandomNumberGenerator& /*rng*/, bool /*strong*/) const {
   return true;
}
 
std::unique_ptr<Private_Key> Classic_McEliece_PublicKey::generate_another(RandomNumberGenerator& rng) const {
   return std::make_unique<Classic_McEliece_PrivateKey>(rng, m_public->params().parameter_set());
}
 
std::unique_ptr<PK_Ops::KEM_Encryption> Classic_McEliece_PublicKey::create_kem_encryption_op(
   std::string_view params, std::string_view provider) const {
   if(provider.empty() || provider == "base") {
      return std::make_unique<Classic_McEliece_Encryptor>(this->m_public, params);
   }
   throw Provider_Not_Found(algo_name(), provider);
}
 
Classic_McEliece_PrivateKey::Classic_McEliece_PrivateKey(RandomNumberGenerator& rng,
                                                         Classic_McEliece_Parameter_Set param_set) {
   auto params = Classic_McEliece_Parameters::create(param_set);
   const auto seed = rng.random_vec<CmceInitialSeed>(params.seed_len());
   CT::poison(seed);
   std::tie(m_private, m_public) = Classic_McEliece_KeyPair_Internal::generate(params, seed).decompose_to_pair();
 
   BOTAN_ASSERT_NONNULL(m_private);
   BOTAN_ASSERT_NONNULL(m_public);
   CT::unpoison_all(*m_private, *m_public);
}
 
Classic_McEliece_PrivateKey::Classic_McEliece_PrivateKey(std::span<const uint8_t> sk,
                                                         Classic_McEliece_Parameter_Set param_set) {
   auto scope = CT::scoped_poison(sk);
   auto params = Classic_McEliece_Parameters::create(param_set);
   auto sk_internal = Classic_McEliece_PrivateKeyInternal::from_bytes(params, sk);
   m_private = std::make_shared<Classic_McEliece_PrivateKeyInternal>(std::move(sk_internal));
   // This creates and loads the public key, which is very large. Potentially, we could only load
   // it on demand (since one may use the private key only for decapsulation without needing the public key).
   // TODO: consider building a load-on-demand mechanism for the public key
   m_public = Classic_McEliece_PublicKeyInternal::create_from_private_key(*m_private);
   CT::unpoison_all(*m_public, *m_private);
}
 
Classic_McEliece_PrivateKey::Classic_McEliece_PrivateKey(const AlgorithmIdentifier& alg_id,
                                                         std::span<const uint8_t> key_bits) :
      Classic_McEliece_PrivateKey(key_bits, Classic_McEliece_Parameter_Set::from_oid(alg_id.oid())) {
   // The parameter set is identified by the OID; no parameters are defined.
   if(!alg_id.parameters_are_empty()) {
      throw Decoding_Error("Unexpected parameters for Classic McEliece private key");
   }
}
 
std::unique_ptr<Public_Key> Classic_McEliece_PrivateKey::public_key() const {
   return std::make_unique<Classic_McEliece_PublicKey>(*this);
}
 
secure_vector<uint8_t> Classic_McEliece_PrivateKey::private_key_bits() const {
   return raw_private_key_bits();
}
 
secure_vector<uint8_t> Classic_McEliece_PrivateKey::raw_private_key_bits() const {
   return m_private->serialize();
}
 
bool Classic_McEliece_PrivateKey::check_key(RandomNumberGenerator& /*rng*/, bool /*strong*/) const {
   return m_private->check_key();
}
 
std::unique_ptr<PK_Ops::KEM_Decryption> Classic_McEliece_PrivateKey::create_kem_decryption_op(
   RandomNumberGenerator& rng, std::string_view params, std::string_view provider) const {
   BOTAN_UNUSED(rng);
   if(provider.empty() || provider == "base") {
      return std::make_unique<Classic_McEliece_Decryptor>(this->m_private, params);
   }
   throw Provider_Not_Found(algo_name(), provider);
}
 
}  // namespace Botan