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/**
* (C) Copyright Projet SECRET, INRIA, Rocquencourt
* (C) Bhaskar Biswas and Nicolas Sendrier
*
* (C) 2014 cryptosource GmbH
* (C) 2014 Falko Strenzke fstrenzke@cryptosource.de
*
* Distributed under the terms of the Botan license
*
*/
#include <botan/mceliece_key.h>
#include <botan/internal/bit_ops.h>
#include <botan/gf2m_small_m.h>
#include <botan/mceliece.h>
#include <botan/internal/code_based_key_gen.h>
#include <botan/alg_id.h>
#include <botan/der_enc.h>
#include <botan/ber_dec.h>
#include <botan/oids.h>
namespace Botan {
McEliece_PrivateKey::McEliece_PrivateKey(polyn_gf2m const& goppa_polyn,
std::vector<u32bit> const& parity_check_matrix_coeffs,
std::vector<polyn_gf2m> const& square_root_matrix,
std::vector<gf2m> const& inverse_support,
std::vector<byte> const& public_matrix) :
McEliece_PublicKey(public_matrix, goppa_polyn.get_degree(), inverse_support.size()),
m_g(goppa_polyn),
m_sqrtmod(square_root_matrix),
m_Linv(inverse_support),
m_coeffs(parity_check_matrix_coeffs),
m_codimension(ceil_log2(inverse_support.size()) * goppa_polyn.get_degree()),
m_dimension(inverse_support.size() - m_codimension)
{
};
McEliece_PrivateKey::McEliece_PrivateKey(RandomNumberGenerator& rng, size_t code_length, size_t t)
{
u32bit ext_deg = ceil_log2(code_length);
*this = generate_mceliece_key(rng, ext_deg, code_length, t);
}
unsigned McEliece_PublicKey::get_message_word_bit_length() const
{
u32bit codimension = ceil_log2(m_code_length) * m_t;
return m_code_length - codimension;
}
AlgorithmIdentifier McEliece_PublicKey::algorithm_identifier() const
{
return AlgorithmIdentifier(get_oid(), std::vector<byte>());
}
std::vector<byte> McEliece_PublicKey::x509_subject_public_key() const
{
// encode the public key
return unlock(DER_Encoder()
.start_cons(SEQUENCE)
.start_cons(SEQUENCE)
.encode(static_cast<size_t>(get_code_length()))
.encode(static_cast<size_t>(get_t()))
.end_cons()
.encode(m_public_matrix, OCTET_STRING)
.end_cons()
.get_contents());
}
McEliece_PublicKey::McEliece_PublicKey(const McEliece_PublicKey & other) :
m_public_matrix(other.m_public_matrix),
m_t(other.m_t),
m_code_length(other.m_code_length)
{
}
McEliece_PublicKey::McEliece_PublicKey(const std::vector<byte>& key_bits)
{
BER_Decoder dec(key_bits);
size_t n;
size_t t;
dec.start_cons(SEQUENCE)
.start_cons(SEQUENCE)
.decode(n)
.decode(t)
.end_cons()
.decode(m_public_matrix, OCTET_STRING)
.end_cons();
m_t = t;
m_code_length = n;
}
secure_vector<byte> McEliece_PrivateKey::pkcs8_private_key() const
{
DER_Encoder enc;
enc.start_cons(SEQUENCE)
.start_cons(SEQUENCE)
.encode(static_cast<size_t>(get_code_length()))
.encode(static_cast<size_t>(get_t()))
.end_cons()
.encode(m_public_matrix, OCTET_STRING)
.encode(m_g.encode(), OCTET_STRING); // g as octet string
enc.start_cons(SEQUENCE);
for(u32bit i = 0; i < m_sqrtmod.size(); i++)
{
enc.encode(m_sqrtmod[i].encode(), OCTET_STRING);
}
enc.end_cons();
secure_vector<byte> enc_support;
for(u32bit i = 0; i < m_Linv.size(); i++)
{
enc_support.push_back(m_Linv[i] >> 8);
enc_support.push_back(m_Linv[i]);
}
enc.encode(enc_support, OCTET_STRING);
secure_vector<byte> enc_H;
for(u32bit i = 0; i < m_coeffs.size(); i++)
{
enc_H.push_back(m_coeffs[i] >> 24);
enc_H.push_back(m_coeffs[i] >> 16);
enc_H.push_back(m_coeffs[i] >> 8);
enc_H.push_back(m_coeffs[i]);
}
enc.encode(enc_H, OCTET_STRING);
enc.end_cons();
return enc.get_contents();
}
bool McEliece_PrivateKey::check_key(RandomNumberGenerator& rng, bool) const
{
const McEliece_PublicKey* p_pk = dynamic_cast<const McEliece_PublicKey*>(this);
McEliece_Private_Operation priv_op(*this);
McEliece_Public_Operation pub_op(*p_pk, p_pk->get_code_length() );
secure_vector<byte> plaintext((p_pk->get_message_word_bit_length()+7)/8);
rng.randomize(&plaintext[0], plaintext.size() - 1);
secure_vector<gf2m> err_pos = create_random_error_positions(p_pk->get_code_length(), p_pk->get_t(), rng);
mceliece_message_parts parts(err_pos, plaintext, p_pk->get_code_length());
secure_vector<byte> message_and_error_input = parts.get_concat();
secure_vector<byte> ciphertext = pub_op.encrypt(&message_and_error_input[0], message_and_error_input.size(), rng);
secure_vector<byte> message_and_error_output = priv_op.decrypt(&ciphertext[0], ciphertext.size() );
return (message_and_error_input == message_and_error_output);
}
McEliece_PrivateKey::McEliece_PrivateKey(const secure_vector<byte>& key_bits)
{
size_t n, t;
secure_vector<byte> g_enc;
BER_Decoder dec_base(key_bits);
BER_Decoder dec = dec_base.start_cons(SEQUENCE)
.start_cons(SEQUENCE)
.decode(n)
.decode(t)
.end_cons()
.decode(m_public_matrix, OCTET_STRING)
.decode(g_enc, OCTET_STRING);
if(t == 0 || n == 0)
throw Decoding_Error("invalid McEliece parameters");
u32bit ext_deg = ceil_log2(n);
m_code_length = n;
m_t = t;
m_codimension = (ext_deg * t);
m_dimension = (n - m_codimension);
std::shared_ptr<gf2m_small_m::Gf2m_Field> sp_field(new gf2m_small_m::Gf2m_Field(ext_deg));
m_g = polyn_gf2m(g_enc, sp_field);
if(m_g.get_degree() != static_cast<int>(t))
{
throw Decoding_Error("degree of decoded Goppa polynomial is incorrect");
}
BER_Decoder dec2 = dec.start_cons(SEQUENCE);
for(u32bit i = 0; i < t/2; i++)
{
secure_vector<byte> sqrt_enc;
dec2.decode(sqrt_enc, OCTET_STRING);
while(sqrt_enc.size() < (t*2))
{
// ensure that the length is always t
sqrt_enc.push_back(0);
sqrt_enc.push_back(0);
}
if(sqrt_enc.size() != t*2)
{
throw Decoding_Error("length of square root polynomial entry is too large");
}
m_sqrtmod.push_back(polyn_gf2m(sqrt_enc, sp_field));
}
secure_vector<byte> enc_support;
BER_Decoder dec3 = dec2.end_cons()
.decode(enc_support, OCTET_STRING);
if(enc_support.size() % 2)
{
throw Decoding_Error("encoded support has odd length");
}
if(enc_support.size() / 2 != n)
{
throw Decoding_Error("encoded support has length different from code length");
}
for(u32bit i = 0; i < n*2; i+=2)
{
gf2m el = (enc_support[i] << 8) | enc_support[i+1];
m_Linv.push_back(el);
}
secure_vector<byte> enc_H;
dec3.decode(enc_H, OCTET_STRING)
.end_cons();
if(enc_H.size() % 4)
{
throw Decoding_Error("encoded parity check matrix has length which is not a multiple of four");
}
if(enc_H.size()/4 != bit_size_to_32bit_size(m_codimension) * m_code_length )
{
throw Decoding_Error("encoded parity check matrix has wrong length");
}
for(u32bit i = 0; i < enc_H.size(); i+=4)
{
u32bit coeff = (enc_H[i] << 24) | (enc_H[i+1] << 16) | (enc_H[i+2] << 8) | enc_H[i+3];
m_coeffs.push_back(coeff);
}
}
bool McEliece_PrivateKey::operator==(const McEliece_PrivateKey & other) const
{
if(*static_cast<const McEliece_PublicKey*>(this) != *static_cast<const McEliece_PublicKey*>(&other))
{
return false;
}
if(m_g != other.m_g)
{
return false;
}
if( m_sqrtmod != other.m_sqrtmod)
{
return false;
}
if( m_Linv != other.m_Linv)
{
return false;
}
if( m_coeffs != other.m_coeffs)
{
return false;
}
if(m_codimension != other.m_codimension || m_dimension != other.m_dimension)
{
return false;
}
return true;
}
bool McEliece_PublicKey::operator==(const McEliece_PublicKey& other) const
{
if(m_public_matrix != other.m_public_matrix)
{
return false;
}
if(m_t != other.m_t )
{
return false;
}
if( m_code_length != other.m_code_length)
{
return false;
}
return true;
}
}
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