5111374265

Committed 29 May 2023 11:19AM UTC coverage: 92.227% (+0.5%) from 91.723%

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95.96

/src/lib/pubkey/mce/goppa_code.cpp

/*
 * (C) Copyright Projet SECRET, INRIA, Rocquencourt
 * (C) Bhaskar Biswas and  Nicolas Sendrier
 *
 * (C) 2014 cryptosource GmbH
 * (C) 2014 Falko Strenzke fstrenzke@cryptosource.de
 *
 * Botan is released under the Simplified BSD License (see license.txt)
 *
 */

#include <botan/internal/mce_internal.h>

#include <botan/internal/code_based_util.h>

namespace Botan {

namespace {

void matrix_arr_mul(std::vector<uint32_t> matrix,
                    size_t numo_rows,
                    size_t words_per_row,
                    const uint8_t input_vec[],
                    uint32_t output_vec[],
                    size_t output_vec_len) {
   for(size_t j = 0; j < numo_rows; j++) {
      if((input_vec[j / 8] >> (j % 8)) & 1) {
         for(size_t i = 0; i < output_vec_len; i++) {
            output_vec[i] ^= matrix[j * (words_per_row) + i];
         }
      }
   }
}

/**
* returns the error vector to the syndrome
*/
secure_vector<gf2m> goppa_decode(const polyn_gf2m& syndrom_polyn,
                                 const polyn_gf2m& g,
                                 const std::vector<polyn_gf2m>& sqrtmod,
                                 const std::vector<gf2m>& Linv) {
   const size_t code_length = Linv.size();
   gf2m a;
   uint32_t t = g.get_degree();

   std::shared_ptr<GF2m_Field> sp_field = g.get_sp_field();

   std::pair<polyn_gf2m, polyn_gf2m> h_aux = polyn_gf2m::eea_with_coefficients(syndrom_polyn, g, 1);
   polyn_gf2m& h = h_aux.first;
   polyn_gf2m& aux = h_aux.second;
   a = sp_field->gf_inv(aux.get_coef(0));
   gf2m log_a = sp_field->gf_log(a);
   for(int i = 0; i <= h.get_degree(); ++i) {
      h.set_coef(i, sp_field->gf_mul_zrz(log_a, h.get_coef(i)));
   }

   //  compute h(z) += z
   h.add_to_coef(1, 1);
   // compute S square root of h (using sqrtmod)
   polyn_gf2m S(t - 1, g.get_sp_field());

   for(uint32_t i = 0; i < t; i++) {
      a = sp_field->gf_sqrt(h.get_coef(i));

      if(i & 1) {
         for(uint32_t j = 0; j < t; j++) {
            S.add_to_coef(j, sp_field->gf_mul(a, sqrtmod[i / 2].get_coef(j)));
         }
      } else {
         S.add_to_coef(i / 2, a);
      }
   } /* end for loop (i) */

   S.get_degree();

   std::pair<polyn_gf2m, polyn_gf2m> v_u = polyn_gf2m::eea_with_coefficients(S, g, t / 2 + 1);
   polyn_gf2m& u = v_u.second;
   polyn_gf2m& v = v_u.first;

   // sigma = u^2+z*v^2
   polyn_gf2m sigma(t, g.get_sp_field());

   const int u_deg = u.get_degree();
   BOTAN_ASSERT(u_deg >= 0, "Valid degree");
   for(int i = 0; i <= u_deg; ++i) {
      sigma.set_coef(2 * i, sp_field->gf_square(u.get_coef(i)));
   }

   const int v_deg = v.get_degree();
   BOTAN_ASSERT(v_deg >= 0, "Valid degree");
   for(int i = 0; i <= v_deg; ++i) {
      sigma.set_coef(2 * i + 1, sp_field->gf_square(v.get_coef(i)));
   }

   secure_vector<gf2m> res = find_roots_gf2m_decomp(sigma, code_length);
   size_t d = res.size();

   secure_vector<gf2m> result(d);
   for(uint32_t i = 0; i < d; ++i) {
      gf2m current = res[i];

      gf2m tmp;
      tmp = gray_to_lex(current);
      /// XXX double assignment, possible bug?
      if(tmp >= code_length) /* invalid root */
      {
         result[i] = static_cast<gf2m>(i);
      }
      result[i] = Linv[tmp];
   }

   return result;
}
}  // namespace

void mceliece_decrypt(secure_vector<uint8_t>& plaintext_out,
                      secure_vector<uint8_t>& error_mask_out,
                      const secure_vector<uint8_t>& ciphertext,
                      const McEliece_PrivateKey& key) {
   mceliece_decrypt(plaintext_out, error_mask_out, ciphertext.data(), ciphertext.size(), key);
}

void mceliece_decrypt(secure_vector<uint8_t>& plaintext,
                      secure_vector<uint8_t>& error_mask,
                      const uint8_t ciphertext[],
                      size_t ciphertext_len,
                      const McEliece_PrivateKey& key) {
   secure_vector<gf2m> error_pos;
   plaintext = mceliece_decrypt(error_pos, ciphertext, ciphertext_len, key);

   const size_t code_length = key.get_code_length();
   secure_vector<uint8_t> result((code_length + 7) / 8);
   for(auto&& pos : error_pos) {
      if(pos > code_length) {
         throw Invalid_Argument("error position larger than code size");
      }
      result[pos / 8] |= (1 << (pos % 8));
   }

   error_mask = result;
}

/**
* @p p_err_pos_len must point to the available length of @p error_pos on input, the
* function will set it to the actual number of errors returned in the @p error_pos
* array */
secure_vector<uint8_t> mceliece_decrypt(secure_vector<gf2m>& error_pos,
                                        const uint8_t* ciphertext,
                                        size_t ciphertext_len,
                                        const McEliece_PrivateKey& key) {
   const size_t dimension = key.get_dimension();
   const size_t codimension = key.get_codimension();
   const uint32_t t = key.get_goppa_polyn().get_degree();
   polyn_gf2m syndrome_polyn(key.get_goppa_polyn().get_sp_field());  // init as zero polyn
   const unsigned unused_pt_bits = dimension % 8;
   const uint8_t unused_pt_bits_mask = (1 << unused_pt_bits) - 1;

   if(ciphertext_len != (key.get_code_length() + 7) / 8) {
      throw Invalid_Argument("wrong size of McEliece ciphertext");
   }
   const size_t cleartext_len = (key.get_message_word_bit_length() + 7) / 8;

   if(cleartext_len != bit_size_to_byte_size(dimension)) {
      throw Invalid_Argument("mce-decryption: wrong length of cleartext buffer");
   }

   secure_vector<uint32_t> syndrome_vec(bit_size_to_32bit_size(codimension));
   matrix_arr_mul(key.get_H_coeffs(),
                  key.get_code_length(),
                  bit_size_to_32bit_size(codimension),
                  ciphertext,
                  syndrome_vec.data(),
                  syndrome_vec.size());

   secure_vector<uint8_t> syndrome_byte_vec(bit_size_to_byte_size(codimension));
   const size_t syndrome_byte_vec_size = syndrome_byte_vec.size();
   for(size_t i = 0; i < syndrome_byte_vec_size; i++) {
      syndrome_byte_vec[i] = static_cast<uint8_t>(syndrome_vec[i / 4] >> (8 * (i % 4)));
   }

   syndrome_polyn = polyn_gf2m(
      t - 1, syndrome_byte_vec.data(), bit_size_to_byte_size(codimension), key.get_goppa_polyn().get_sp_field());

   syndrome_polyn.get_degree();
   error_pos = goppa_decode(syndrome_polyn, key.get_goppa_polyn(), key.get_sqrtmod(), key.get_Linv());

   const size_t nb_err = error_pos.size();

   secure_vector<uint8_t> cleartext(cleartext_len);
   copy_mem(cleartext.data(), ciphertext, cleartext_len);

   for(size_t i = 0; i < nb_err; i++) {
      gf2m current = error_pos[i];

      if(current >= cleartext_len * 8) {
         // an invalid position, this shouldn't happen
         continue;
      }
      cleartext[current / 8] ^= (1 << (current % 8));
   }

   if(unused_pt_bits) {
      cleartext[cleartext_len - 1] &= unused_pt_bits_mask;
   }

   return cleartext;
}

}  // namespace Botan

1	/*
2	* (C) Copyright Projet SECRET, INRIA, Rocquencourt
3	* (C) Bhaskar Biswas and Nicolas Sendrier
4	*
5	* (C) 2014 cryptosource GmbH
6	* (C) 2014 Falko Strenzke fstrenzke@cryptosource.de
7	*
8	* Botan is released under the Simplified BSD License (see license.txt)
9	*
10	*/
11
12	#include <botan/internal/mce_internal.h>
13
14	#include <botan/internal/code_based_util.h>
15
16	namespace Botan {
17
18	namespace {
19
20	void matrix_arr_mul(std::vector<uint32_t> matrix,	2,646✔
21	size_t numo_rows,
22	size_t words_per_row,
23	const uint8_t input_vec[],
24	uint32_t output_vec[],
25	size_t output_vec_len) {
26	for(size_t j = 0; j < numo_rows; j++) {	3,633,526✔
27	if((input_vec[j / 8] >> (j % 8)) & 1) {	3,630,880✔
28	for(size_t i = 0; i < output_vec_len; i++) {	43,612,911✔
29	output_vec[i] ^= matrix[j * (words_per_row) + i];	41,796,930✔
30	}
31	}
32	}
33	}	2,646✔
34
35	/**
36	* returns the error vector to the syndrome
37	*/
38	secure_vector<gf2m> goppa_decode(const polyn_gf2m& syndrom_polyn,	2,646✔
39	const polyn_gf2m& g,
40	const std::vector<polyn_gf2m>& sqrtmod,
41	const std::vector<gf2m>& Linv) {
42	const size_t code_length = Linv.size();	2,646✔
43	gf2m a;	2,646✔
44	uint32_t t = g.get_degree();	2,646✔
45
46	std::shared_ptr<GF2m_Field> sp_field = g.get_sp_field();	2,646✔
47
48	std::pair<polyn_gf2m, polyn_gf2m> h_aux = polyn_gf2m::eea_with_coefficients(syndrom_polyn, g, 1);	2,646✔
49	polyn_gf2m& h = h_aux.first;	2,646✔
50	polyn_gf2m& aux = h_aux.second;	2,646✔
51	a = sp_field->gf_inv(aux.get_coef(0));	2,646✔
52	gf2m log_a = sp_field->gf_log(a);	2,646✔
53	for(int i = 0; i <= h.get_degree(); ++i) {	84,278✔
54	h.set_coef(i, sp_field->gf_mul_zrz(log_a, h.get_coef(i)));	163,184✔
55	}
56
57	// compute h(z) += z
58	h.add_to_coef(1, 1);	2,646✔
59	// compute S square root of h (using sqrtmod)
60	polyn_gf2m S(t - 1, g.get_sp_field());	2,646✔
61
62	for(uint32_t i = 0; i < t; i++) {	84,285✔
63	a = sp_field->gf_sqrt(h.get_coef(i));	81,639✔
64
65	if(i & 1) {	81,639✔
66	for(uint32_t j = 0; j < t; j++) {	2,144,892✔
67	S.add_to_coef(j, sp_field->gf_mul(a, sqrtmod[i / 2].get_coef(j)));	4,208,446✔
68	}
69	} else {
70	S.add_to_coef(i / 2, a);	81,639✔
71	}
72	} /* end for loop (i) */
73
74	S.get_degree();	2,646✔
75
76	std::pair<polyn_gf2m, polyn_gf2m> v_u = polyn_gf2m::eea_with_coefficients(S, g, t / 2 + 1);	2,646✔
77	polyn_gf2m& u = v_u.second;	2,646✔
78	polyn_gf2m& v = v_u.first;	2,646✔
79
80	// sigma = u^2+z*v^2
81	polyn_gf2m sigma(t, g.get_sp_field());	2,646✔
82
83	const int u_deg = u.get_degree();	2,646✔
84	BOTAN_ASSERT(u_deg >= 0, "Valid degree");	2,646✔
85	for(int i = 0; i <= u_deg; ++i) {	45,424✔
86	sigma.set_coef(2 * i, sp_field->gf_square(u.get_coef(i)));	42,778✔
87	}
88
89	const int v_deg = v.get_degree();	2,646✔
90	BOTAN_ASSERT(v_deg >= 0, "Valid degree");	2,646✔
91	for(int i = 0; i <= v_deg; ++i) {	44,152✔
92	sigma.set_coef(2 * i + 1, sp_field->gf_square(v.get_coef(i)));	41,506✔
93	}
94
95	secure_vector<gf2m> res = find_roots_gf2m_decomp(sigma, code_length);	2,646✔
96	size_t d = res.size();	2,646✔
97
98	secure_vector<gf2m> result(d);	2,646✔
99	for(uint32_t i = 0; i < d; ++i) {	84,285✔
100	gf2m current = res[i];	81,639✔
101
102	gf2m tmp;	81,639✔
103	tmp = gray_to_lex(current);	81,639✔
104	/// XXX double assignment, possible bug?
105	if(tmp >= code_length) /* invalid root */	81,639✔
106	{
107	result[i] = static_cast<gf2m>(i);	×
108	}
109	result[i] = Linv[tmp];	81,639✔
110	}
111
112	return result;	2,646✔
113	}	10,584✔
114	} // namespace
115
116	void mceliece_decrypt(secure_vector<uint8_t>& plaintext_out,	85✔
117	secure_vector<uint8_t>& error_mask_out,
118	const secure_vector<uint8_t>& ciphertext,
119	const McEliece_PrivateKey& key) {
120	mceliece_decrypt(plaintext_out, error_mask_out, ciphertext.data(), ciphertext.size(), key);	85✔
121	}	85✔
122
123	void mceliece_decrypt(secure_vector<uint8_t>& plaintext,	2,646✔
124	secure_vector<uint8_t>& error_mask,
125	const uint8_t ciphertext[],
126	size_t ciphertext_len,
127	const McEliece_PrivateKey& key) {
128	secure_vector<gf2m> error_pos;	2,646✔
129	plaintext = mceliece_decrypt(error_pos, ciphertext, ciphertext_len, key);	5,292✔
130
131	const size_t code_length = key.get_code_length();	2,646✔
132	secure_vector<uint8_t> result((code_length + 7) / 8);	2,646✔
133	for(auto&& pos : error_pos) {	84,285✔
134	if(pos > code_length) {	81,639✔
135	throw Invalid_Argument("error position larger than code size");	×
136	}
137	result[pos / 8] \|= (1 << (pos % 8));	81,639✔
138	}
139
140	error_mask = result;	2,646✔
141	}	5,292✔
142
143	/**
144	* @p p_err_pos_len must point to the available length of @p error_pos on input, the
145	* function will set it to the actual number of errors returned in the @p error_pos
146	* array */
147	secure_vector<uint8_t> mceliece_decrypt(secure_vector<gf2m>& error_pos,	2,646✔
148	const uint8_t* ciphertext,
149	size_t ciphertext_len,
150	const McEliece_PrivateKey& key) {
151	const size_t dimension = key.get_dimension();	2,646✔
152	const size_t codimension = key.get_codimension();	2,646✔
153	const uint32_t t = key.get_goppa_polyn().get_degree();	2,646✔
154	polyn_gf2m syndrome_polyn(key.get_goppa_polyn().get_sp_field()); // init as zero polyn	2,646✔
155	const unsigned unused_pt_bits = dimension % 8;	2,646✔
156	const uint8_t unused_pt_bits_mask = (1 << unused_pt_bits) - 1;	2,646✔
157
158	if(ciphertext_len != (key.get_code_length() + 7) / 8) {	2,646✔
159	throw Invalid_Argument("wrong size of McEliece ciphertext");	×
160	}
161	const size_t cleartext_len = (key.get_message_word_bit_length() + 7) / 8;	2,646✔
162
163	if(cleartext_len != bit_size_to_byte_size(dimension)) {	2,646✔
164	throw Invalid_Argument("mce-decryption: wrong length of cleartext buffer");	×
165	}
166
167	secure_vector<uint32_t> syndrome_vec(bit_size_to_32bit_size(codimension));	2,646✔
168	matrix_arr_mul(key.get_H_coeffs(),	2,646✔
169	key.get_code_length(),
170	bit_size_to_32bit_size(codimension),
171	ciphertext,
172	syndrome_vec.data(),
173	syndrome_vec.size());
174
175	secure_vector<uint8_t> syndrome_byte_vec(bit_size_to_byte_size(codimension));	2,646✔
176	const size_t syndrome_byte_vec_size = syndrome_byte_vec.size();	2,646✔
177	for(size_t i = 0; i < syndrome_byte_vec_size; i++) {	113,626✔
178	syndrome_byte_vec[i] = static_cast<uint8_t>(syndrome_vec[i / 4] >> (8 * (i % 4)));	110,980✔
179	}
180
181	syndrome_polyn = polyn_gf2m(	2,646✔
182	t - 1, syndrome_byte_vec.data(), bit_size_to_byte_size(codimension), key.get_goppa_polyn().get_sp_field());	5,292✔
183
184	syndrome_polyn.get_degree();	2,646✔
185	error_pos = goppa_decode(syndrome_polyn, key.get_goppa_polyn(), key.get_sqrtmod(), key.get_Linv());	5,292✔
186
187	const size_t nb_err = error_pos.size();	2,646✔
188
189	secure_vector<uint8_t> cleartext(cleartext_len);	2,646✔
190	copy_mem(cleartext.data(), ciphertext, cleartext_len);	2,646✔
191
192	for(size_t i = 0; i < nb_err; i++) {	84,285✔
193	gf2m current = error_pos[i];	81,639✔
194
195	if(current >= cleartext_len * 8) {	81,639✔
196	// an invalid position, this shouldn't happen
197	continue;	21,994✔
198	}
199	cleartext[current / 8] ^= (1 << (current % 8));	59,645✔
200	}
201
202	if(unused_pt_bits) {	2,646✔
203	cleartext[cleartext_len - 1] &= unused_pt_bits_mask;	1,933✔
204	}
205
206	return cleartext;	5,292✔
207	}	5,292✔
208
209	} // namespace Botan

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