Botan::Kyber_Expanded_Keypair_Codec Class Reference

#include <kyber_round3_impl.h>

Inheritance diagram for Botan::Kyber_Expanded_Keypair_Codec:

Public Member Functions
KyberInternalKeypair	decode_keypair (std::span< const uint8_t > buffer, KyberConstants mode) const override
secure_vector< uint8_t >	encode_keypair (KyberInternalKeypair private_key) const override

Detailed Description

Definition at line 56 of file kyber_round3_impl.h.

Member Function Documentation

decode_keypair()

KyberInternalKeypair Botan::Kyber_Expanded_Keypair_Codec::decode_keypair ( std::span< const uint8_t > sk, KyberConstants mode ) const

overridevirtual

Key decoding as specified in Crystals Kyber (Version 3.01), Algorithms 4 (CPAPKE.KeyGen()), and 7 (CCAKEM.KeyGen())

Public Key: pk := (encode(t) || rho) Secret Key: sk' := encode(s)

Expanded Secret Key: sk := (sk' || pk || H(pk) || z)

Implements Botan::Kyber_Keypair_Codec.

Definition at line 74 of file kyber_round3_impl.cpp.

                                                                                             {
   auto scope = CT::scoped_poison(sk);
   BufferSlicer s(sk);
 
   auto skpv = Kyber_Algos::decode_polynomial_vector(s.take(mode.polynomial_vector_bytes()), mode);
   auto pub_key = s.copy<KyberSerializedPublicKey>(mode.public_key_bytes());
   auto puk_key_hash = s.take<KyberHashedPublicKey>(KyberConstants::PUBLIC_KEY_HASH_BYTES);
   auto z = s.copy<KyberImplicitRejectionValue>(KyberConstants::SEED_BYTES);
 
   BOTAN_ASSERT_NOMSG(s.empty());
 
   CT::unpoison_all(pub_key, puk_key_hash, skpv, z);
 
   KyberInternalKeypair keypair{
      std::make_shared<Kyber_PublicKeyInternal>(mode, std::move(pub_key)),
      std::make_shared<Kyber_PrivateKeyInternal>(
         std::move(mode),
         std::move(skpv),
         KyberPrivateKeySeed{std::nullopt,  // Reading from an expanded and encoded
                                            // private key cannot reconstruct the
                                            // original seed from key generation.
                             std::move(z)}),
   };
 
   BOTAN_ASSERT(keypair.first && keypair.second, "reading private key encoding");
   BOTAN_ARG_CHECK(keypair.first->H_public_key_bits_raw().size() == puk_key_hash.size() &&
                      std::equal(keypair.first->H_public_key_bits_raw().begin(),
                                 keypair.first->H_public_key_bits_raw().end(),
                                 puk_key_hash.begin()),
                   "public key's hash does not match the stored hash");
 
   return keypair;
}

References BOTAN_ARG_CHECK, BOTAN_ASSERT, BOTAN_ASSERT_NOMSG, Botan::BufferSlicer::copy(), Botan::Kyber_Algos::decode_polynomial_vector(), Botan::BufferSlicer::empty(), Botan::KyberConstants::polynomial_vector_bytes(), Botan::KyberConstants::public_key_bytes(), Botan::KyberConstants::PUBLIC_KEY_HASH_BYTES, Botan::CT::scoped_poison(), Botan::KyberConstants::SEED_BYTES, Botan::BufferSlicer::take(), and Botan::CT::unpoison_all().

encode_keypair()

secure_vector< uint8_t > Botan::Kyber_Expanded_Keypair_Codec::encode_keypair ( KyberInternalKeypair private_key ) const

overridevirtual

Implements Botan::Kyber_Keypair_Codec.

Definition at line 109 of file kyber_round3_impl.cpp.

                                                                                                      {
   BOTAN_ASSERT_NONNULL(keypair.first);
   BOTAN_ASSERT_NONNULL(keypair.second);
   const auto& mode = keypair.first->mode();
   auto scope = CT::scoped_poison(*keypair.second);
   auto result = concat(Kyber_Algos::encode_polynomial_vector(keypair.second->s().reduce(), mode),
                        keypair.first->public_key_bits_raw(),
                        keypair.first->H_public_key_bits_raw(),
                        keypair.second->z());
   CT::unpoison(result);
   return result;
}

References BOTAN_ASSERT_NONNULL, Botan::concat(), Botan::Kyber_Algos::encode_polynomial_vector(), Botan::CT::scoped_poison(), and Botan::CT::unpoison().

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The documentation for this class was generated from the following files:

• src/lib/pubkey/kyber/kyber_round3/kyber_round3_impl.h
• src/lib/pubkey/kyber/kyber_round3/kyber_round3_impl.cpp