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402 lines
10 KiB
402 lines
10 KiB
/*
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* Wrapper for implementing the PQClean API.
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*/
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#include <string.h>
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#include "randombytes.h"
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#include "falcon.h"
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#include "inner.h"
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#include "rpo.h"
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#define NONCELEN 40
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/*
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* Encoding formats (nnnn = log of degree, 9 for Falcon-512, 10 for Falcon-1024)
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*
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* private key:
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* header byte: 0101nnnn
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* private f (6 or 5 bits by element, depending on degree)
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* private g (6 or 5 bits by element, depending on degree)
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* private F (8 bits by element)
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*
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* public key:
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* header byte: 0000nnnn
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* public h (14 bits by element)
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*
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* signature:
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* header byte: 0011nnnn
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* nonce 40 bytes
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* value (12 bits by element)
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*
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* message + signature:
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* signature length (2 bytes, big-endian)
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* nonce 40 bytes
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* message
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* header byte: 0010nnnn
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* value (12 bits by element)
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* (signature length is 1+len(value), not counting the nonce)
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*/
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/* see falcon.h */
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int PQCLEAN_FALCON512_CLEAN_crypto_sign_keypair_from_seed_rpo(
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uint8_t *pk,
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uint8_t *sk,
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unsigned char *seed
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) {
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union
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{
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uint8_t b[FALCON_KEYGEN_TEMP_9];
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uint64_t dummy_u64;
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fpr dummy_fpr;
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} tmp;
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int8_t f[512], g[512], F[512];
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uint16_t h[512];
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inner_shake256_context rng;
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size_t u, v;
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/*
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* Generate key pair.
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*/
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inner_shake256_init(&rng);
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inner_shake256_inject(&rng, seed, sizeof seed);
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inner_shake256_flip(&rng);
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PQCLEAN_FALCON512_CLEAN_keygen(&rng, f, g, F, NULL, h, 9, tmp.b);
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inner_shake256_ctx_release(&rng);
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/*
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* Encode private key.
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*/
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sk[0] = 0x50 + 9;
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u = 1;
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v = PQCLEAN_FALCON512_CLEAN_trim_i8_encode(
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sk + u, PQCLEAN_FALCON512_CLEAN_CRYPTO_SECRETKEYBYTES - u,
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f, 9, PQCLEAN_FALCON512_CLEAN_max_fg_bits[9]);
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if (v == 0)
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{
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return -1;
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}
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u += v;
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v = PQCLEAN_FALCON512_CLEAN_trim_i8_encode(
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sk + u, PQCLEAN_FALCON512_CLEAN_CRYPTO_SECRETKEYBYTES - u,
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g, 9, PQCLEAN_FALCON512_CLEAN_max_fg_bits[9]);
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if (v == 0)
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{
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return -1;
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}
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u += v;
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v = PQCLEAN_FALCON512_CLEAN_trim_i8_encode(
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sk + u, PQCLEAN_FALCON512_CLEAN_CRYPTO_SECRETKEYBYTES - u,
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F, 9, PQCLEAN_FALCON512_CLEAN_max_FG_bits[9]);
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if (v == 0)
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{
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return -1;
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}
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u += v;
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if (u != PQCLEAN_FALCON512_CLEAN_CRYPTO_SECRETKEYBYTES)
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{
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return -1;
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}
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/*
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* Encode public key.
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*/
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pk[0] = 0x00 + 9;
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v = PQCLEAN_FALCON512_CLEAN_modq_encode(
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pk + 1, PQCLEAN_FALCON512_CLEAN_CRYPTO_PUBLICKEYBYTES - 1,
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h, 9);
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if (v != PQCLEAN_FALCON512_CLEAN_CRYPTO_PUBLICKEYBYTES - 1)
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{
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return -1;
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}
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return 0;
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}
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int PQCLEAN_FALCON512_CLEAN_crypto_sign_keypair_rpo(
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uint8_t *pk,
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uint8_t *sk
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) {
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unsigned char seed[48];
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/*
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* Generate a random seed.
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*/
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randombytes(seed, sizeof seed);
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return PQCLEAN_FALCON512_CLEAN_crypto_sign_keypair_from_seed_rpo(pk, sk, seed);
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}
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/*
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* Compute the signature. nonce[] receives the nonce and must have length
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* NONCELEN bytes. sigbuf[] receives the signature value (without nonce
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* or header byte), with *sigbuflen providing the maximum value length and
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* receiving the actual value length.
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*
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* If a signature could be computed but not encoded because it would
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* exceed the output buffer size, then a new signature is computed. If
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* the provided buffer size is too low, this could loop indefinitely, so
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* the caller must provide a size that can accommodate signatures with a
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* large enough probability.
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*
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* Return value: 0 on success, -1 on error.
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*/
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static int do_sign(
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uint8_t *nonce,
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uint8_t *sigbuf,
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size_t *sigbuflen,
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const uint8_t *m,
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size_t mlen,
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const uint8_t *sk
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) {
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union
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{
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uint8_t b[72 * 512];
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uint64_t dummy_u64;
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fpr dummy_fpr;
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} tmp;
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int8_t f[512], g[512], F[512], G[512];
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struct
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{
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int16_t sig[512];
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uint16_t hm[512];
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} r;
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unsigned char seed[48];
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inner_shake256_context sc;
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rpo128_context rc;
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size_t u, v;
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/*
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* Decode the private key.
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*/
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if (sk[0] != 0x50 + 9)
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{
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return -1;
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}
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u = 1;
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v = PQCLEAN_FALCON512_CLEAN_trim_i8_decode(
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f, 9, PQCLEAN_FALCON512_CLEAN_max_fg_bits[9],
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sk + u, PQCLEAN_FALCON512_CLEAN_CRYPTO_SECRETKEYBYTES - u);
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if (v == 0)
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{
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return -1;
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}
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u += v;
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v = PQCLEAN_FALCON512_CLEAN_trim_i8_decode(
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g, 9, PQCLEAN_FALCON512_CLEAN_max_fg_bits[9],
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sk + u, PQCLEAN_FALCON512_CLEAN_CRYPTO_SECRETKEYBYTES - u);
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if (v == 0)
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{
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return -1;
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}
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u += v;
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v = PQCLEAN_FALCON512_CLEAN_trim_i8_decode(
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F, 9, PQCLEAN_FALCON512_CLEAN_max_FG_bits[9],
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sk + u, PQCLEAN_FALCON512_CLEAN_CRYPTO_SECRETKEYBYTES - u);
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if (v == 0)
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{
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return -1;
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}
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u += v;
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if (u != PQCLEAN_FALCON512_CLEAN_CRYPTO_SECRETKEYBYTES)
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{
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return -1;
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}
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if (!PQCLEAN_FALCON512_CLEAN_complete_private(G, f, g, F, 9, tmp.b))
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{
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return -1;
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}
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/*
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* Create a random nonce (40 bytes).
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*/
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randombytes(nonce, NONCELEN);
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/* ==== Start: Deviation from the reference implementation ================================= */
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// Transform the nonce into 8 chunks each of size 5 bytes. We do this in order to be sure that
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// the conversion to field elements succeeds
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uint8_t buffer[64];
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memset(buffer, 0, 64);
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for (size_t i = 0; i < 8; i++)
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{
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buffer[8 * i] = nonce[5 * i];
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buffer[8 * i + 1] = nonce[5 * i + 1];
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buffer[8 * i + 2] = nonce[5 * i + 2];
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buffer[8 * i + 3] = nonce[5 * i + 3];
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buffer[8 * i + 4] = nonce[5 * i + 4];
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}
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/*
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* Hash message nonce + message into a vector.
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*/
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rpo128_init(&rc);
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rpo128_absorb(&rc, buffer, NONCELEN + 24);
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rpo128_absorb(&rc, m, mlen);
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rpo128_finalize(&rc);
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PQCLEAN_FALCON512_CLEAN_hash_to_point_rpo(&rc, r.hm, 9);
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rpo128_release(&rc);
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/* ==== End: Deviation from the reference implementation =================================== */
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/*
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* Initialize a RNG.
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*/
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randombytes(seed, sizeof seed);
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inner_shake256_init(&sc);
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inner_shake256_inject(&sc, seed, sizeof seed);
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inner_shake256_flip(&sc);
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/*
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* Compute and return the signature. This loops until a signature
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* value is found that fits in the provided buffer.
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*/
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for (;;)
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{
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PQCLEAN_FALCON512_CLEAN_sign_dyn(r.sig, &sc, f, g, F, G, r.hm, 9, tmp.b);
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v = PQCLEAN_FALCON512_CLEAN_comp_encode(sigbuf, *sigbuflen, r.sig, 9);
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if (v != 0)
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{
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inner_shake256_ctx_release(&sc);
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*sigbuflen = v;
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return 0;
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}
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}
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}
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/*
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* Verify a signature. The nonce has size NONCELEN bytes. sigbuf[]
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* (of size sigbuflen) contains the signature value, not including the
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* header byte or nonce. Return value is 0 on success, -1 on error.
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*/
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static int do_verify(
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const uint8_t *nonce,
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const uint8_t *sigbuf,
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size_t sigbuflen,
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const uint8_t *m,
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size_t mlen,
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const uint8_t *pk
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) {
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union
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{
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uint8_t b[2 * 512];
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uint64_t dummy_u64;
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fpr dummy_fpr;
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} tmp;
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uint16_t h[512], hm[512];
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int16_t sig[512];
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rpo128_context rc;
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/*
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* Decode public key.
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*/
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if (pk[0] != 0x00 + 9)
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{
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return -1;
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}
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if (PQCLEAN_FALCON512_CLEAN_modq_decode(h, 9,
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pk + 1, PQCLEAN_FALCON512_CLEAN_CRYPTO_PUBLICKEYBYTES - 1)
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!= PQCLEAN_FALCON512_CLEAN_CRYPTO_PUBLICKEYBYTES - 1)
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{
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return -1;
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}
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PQCLEAN_FALCON512_CLEAN_to_ntt_monty(h, 9);
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/*
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* Decode signature.
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*/
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if (sigbuflen == 0)
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{
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return -1;
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}
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if (PQCLEAN_FALCON512_CLEAN_comp_decode(sig, 9, sigbuf, sigbuflen) != sigbuflen)
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{
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return -1;
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}
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/* ==== Start: Deviation from the reference implementation ================================= */
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/*
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* Hash nonce + message into a vector.
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*/
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// Transform the nonce into 8 chunks each of size 5 bytes. We do this in order to be sure that
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// the conversion to field elements succeeds
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uint8_t buffer[64];
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memset(buffer, 0, 64);
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for (size_t i = 0; i < 8; i++)
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{
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buffer[8 * i] = nonce[5 * i];
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buffer[8 * i + 1] = nonce[5 * i + 1];
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buffer[8 * i + 2] = nonce[5 * i + 2];
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buffer[8 * i + 3] = nonce[5 * i + 3];
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buffer[8 * i + 4] = nonce[5 * i + 4];
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}
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rpo128_init(&rc);
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rpo128_absorb(&rc, buffer, NONCELEN + 24);
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rpo128_absorb(&rc, m, mlen);
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rpo128_finalize(&rc);
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PQCLEAN_FALCON512_CLEAN_hash_to_point_rpo(&rc, hm, 9);
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rpo128_release(&rc);
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/* === End: Deviation from the reference implementation ==================================== */
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/*
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* Verify signature.
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*/
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if (!PQCLEAN_FALCON512_CLEAN_verify_raw(hm, sig, h, 9, tmp.b))
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{
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return -1;
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}
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return 0;
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}
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/* see falcon.h */
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int PQCLEAN_FALCON512_CLEAN_crypto_sign_signature_rpo(
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uint8_t *sig,
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size_t *siglen,
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const uint8_t *m,
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size_t mlen,
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const uint8_t *sk
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) {
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/*
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* The PQCLEAN_FALCON512_CLEAN_CRYPTO_BYTES constant is used for
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* the signed message object (as produced by crypto_sign())
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* and includes a two-byte length value, so we take care here
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* to only generate signatures that are two bytes shorter than
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* the maximum. This is done to ensure that crypto_sign()
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* and crypto_sign_signature() produce the exact same signature
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* value, if used on the same message, with the same private key,
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* and using the same output from randombytes() (this is for
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* reproducibility of tests).
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*/
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size_t vlen;
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vlen = PQCLEAN_FALCON512_CLEAN_CRYPTO_BYTES - NONCELEN - 3;
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if (do_sign(sig + 1, sig + 1 + NONCELEN, &vlen, m, mlen, sk) < 0)
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{
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return -1;
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}
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sig[0] = 0x30 + 9;
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*siglen = 1 + NONCELEN + vlen;
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return 0;
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}
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/* see falcon.h */
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int PQCLEAN_FALCON512_CLEAN_crypto_sign_verify_rpo(
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const uint8_t *sig,
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size_t siglen,
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const uint8_t *m,
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size_t mlen,
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const uint8_t *pk
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) {
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if (siglen < 1 + NONCELEN)
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{
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return -1;
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}
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if (sig[0] != 0x30 + 9)
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{
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return -1;
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}
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return do_verify(sig + 1, sig + 1 + NONCELEN, siglen - 1 - NONCELEN, m, mlen, pk);
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}
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