301 lines
11 KiB
C
301 lines
11 KiB
C
#include "indcpa.h"
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#include "ntt.h"
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#include "params.h"
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#include "poly.h"
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#include "polyvec.h"
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#include "randombytes.h"
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#include "symmetric.h"
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#include <stdint.h>
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/*************************************************
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* Name: pack_pk
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*
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* Description: Serialize the public key as concatenation of the
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* serialized vector of polynomials pk
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* and the public seed used to generate the matrix A.
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*
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* Arguments: uint8_t *r: pointer to the output serialized public key
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* const poly *pk: pointer to the input public-key polynomial
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* const uint8_t *seed: pointer to the input public seed
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**************************************************/
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static void pack_pk(uint8_t *r, polyvec *pk, const uint8_t *seed) {
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PQCLEAN_KYBER76890S_CLEAN_polyvec_tobytes(r, pk);
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for (size_t i = 0; i < KYBER_SYMBYTES; i++) {
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r[i + KYBER_POLYVECBYTES] = seed[i];
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}
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}
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/*************************************************
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* Name: unpack_pk
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*
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* Description: De-serialize public key from a byte array;
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* approximate inverse of pack_pk
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*
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* Arguments: - polyvec *pk: pointer to output public-key vector of polynomials
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* - uint8_t *seed: pointer to output seed to generate matrix A
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* - const uint8_t *packedpk: pointer to input serialized public key
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**************************************************/
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static void unpack_pk(polyvec *pk, uint8_t *seed, const uint8_t *packedpk) {
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PQCLEAN_KYBER76890S_CLEAN_polyvec_frombytes(pk, packedpk);
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for (size_t i = 0; i < KYBER_SYMBYTES; i++) {
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seed[i] = packedpk[i + KYBER_POLYVECBYTES];
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}
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}
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/*************************************************
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* Name: pack_sk
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*
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* Description: Serialize the secret key
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*
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* Arguments: - uint8_t *r: pointer to output serialized secret key
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* - const polyvec *sk: pointer to input vector of polynomials (secret key)
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**************************************************/
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static void pack_sk(uint8_t *r, polyvec *sk) {
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PQCLEAN_KYBER76890S_CLEAN_polyvec_tobytes(r, sk);
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}
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/*************************************************
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* Name: unpack_sk
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*
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* Description: De-serialize the secret key;
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* inverse of pack_sk
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*
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* Arguments: - polyvec *sk: pointer to output vector of polynomials (secret key)
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* - const uint8_t *packedsk: pointer to input serialized secret key
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**************************************************/
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static void unpack_sk(polyvec *sk, const uint8_t *packedsk) {
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PQCLEAN_KYBER76890S_CLEAN_polyvec_frombytes(sk, packedsk);
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}
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/*************************************************
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* Name: pack_ciphertext
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*
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* Description: Serialize the ciphertext as concatenation of the
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* compressed and serialized vector of polynomials b
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* and the compressed and serialized polynomial v
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*
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* Arguments: uint8_t *r: pointer to the output serialized ciphertext
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* const poly *pk: pointer to the input vector of polynomials b
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* const uint8_t *seed: pointer to the input polynomial v
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**************************************************/
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static void pack_ciphertext(uint8_t *r, polyvec *b, poly *v) {
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PQCLEAN_KYBER76890S_CLEAN_polyvec_compress(r, b);
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PQCLEAN_KYBER76890S_CLEAN_poly_compress(r + KYBER_POLYVECCOMPRESSEDBYTES, v);
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}
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/*************************************************
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* Name: unpack_ciphertext
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*
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* Description: De-serialize and decompress ciphertext from a byte array;
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* approximate inverse of pack_ciphertext
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*
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* Arguments: - polyvec *b: pointer to the output vector of polynomials b
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* - poly *v: pointer to the output polynomial v
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* - const uint8_t *c: pointer to the input serialized ciphertext
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**************************************************/
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static void unpack_ciphertext(polyvec *b, poly *v, const uint8_t *c) {
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PQCLEAN_KYBER76890S_CLEAN_polyvec_decompress(b, c);
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PQCLEAN_KYBER76890S_CLEAN_poly_decompress(v, c + KYBER_POLYVECCOMPRESSEDBYTES);
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}
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/*************************************************
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* Name: rej_uniform
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*
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* Description: Run rejection sampling on uniform random bytes to generate
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* uniform random integers mod q
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*
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* Arguments: - int16_t *r: pointer to output buffer
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* - size_t len: requested number of 16-bit integers (uniform mod q)
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* - const uint8_t *buf: pointer to input buffer (assumed to be uniform random bytes)
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* - size_t buflen: length of input buffer in bytes
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*
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* Returns number of sampled 16-bit integers (at most len)
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**************************************************/
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static size_t rej_uniform(int16_t *r, size_t len, const uint8_t *buf, size_t buflen) {
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size_t ctr, pos;
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uint16_t val;
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ctr = pos = 0;
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while (ctr < len && pos + 2 <= buflen) {
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val = (uint16_t)(buf[pos] | ((uint16_t)buf[pos + 1] << 8));
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pos += 2;
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if (val < 19 * KYBER_Q) {
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val -= (uint16_t)((val >> 12) * KYBER_Q); // Barrett reduction
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r[ctr++] = (int16_t)val;
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}
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}
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return ctr;
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}
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#define gen_a(A,B) gen_matrix(A,B,0)
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#define gen_at(A,B) gen_matrix(A,B,1)
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/*************************************************
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* Name: gen_matrix
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*
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* Description: Deterministically generate matrix A (or the transpose of A)
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* from a seed. Entries of the matrix are polynomials that look
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* uniformly random. Performs rejection sampling on output of
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* a XOF
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*
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* Arguments: - polyvec *a: pointer to ouptput matrix A
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* - const uint8_t *seed: pointer to input seed
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* - int transposed: boolean deciding whether A or A^T is generated
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**************************************************/
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#define MAXNBLOCKS ((530+XOF_BLOCKBYTES)/XOF_BLOCKBYTES) /* 530 is expected number of required bytes */
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static void gen_matrix(polyvec *a, const uint8_t *seed, int transposed) {
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size_t ctr;
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uint8_t i, j;
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uint8_t buf[XOF_BLOCKBYTES * MAXNBLOCKS + 1];
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xof_state state;
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for (i = 0; i < KYBER_K; i++) {
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for (j = 0; j < KYBER_K; j++) {
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if (transposed) {
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xof_absorb(&state, seed, i, j);
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} else {
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xof_absorb(&state, seed, j, i);
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}
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xof_squeezeblocks(buf, MAXNBLOCKS, &state);
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ctr = rej_uniform(a[i].vec[j].coeffs, KYBER_N, buf, MAXNBLOCKS * XOF_BLOCKBYTES);
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while (ctr < KYBER_N) {
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xof_squeezeblocks(buf, 1, &state);
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ctr += rej_uniform(a[i].vec[j].coeffs + ctr, KYBER_N - ctr, buf, XOF_BLOCKBYTES);
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}
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xof_ctx_release(&state);
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}
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}
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}
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/*************************************************
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* Name: indcpa_keypair
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*
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* Description: Generates public and private key for the CPA-secure
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* public-key encryption scheme underlying Kyber
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*
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* Arguments: - uint8_t *pk: pointer to output public key (of length KYBER_INDCPA_PUBLICKEYBYTES bytes)
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* - uint8_t *sk: pointer to output private key (of length KYBER_INDCPA_SECRETKEYBYTES bytes)
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**************************************************/
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void PQCLEAN_KYBER76890S_CLEAN_indcpa_keypair(uint8_t *pk, uint8_t *sk) {
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polyvec a[KYBER_K], e, pkpv, skpv;
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uint8_t buf[2 * KYBER_SYMBYTES];
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uint8_t *publicseed = buf;
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uint8_t *noiseseed = buf + KYBER_SYMBYTES;
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uint8_t nonce = 0;
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randombytes(buf, KYBER_SYMBYTES);
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hash_g(buf, buf, KYBER_SYMBYTES);
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gen_a(a, publicseed);
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for (size_t i = 0; i < KYBER_K; i++) {
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PQCLEAN_KYBER76890S_CLEAN_poly_getnoise(skpv.vec + i, noiseseed, nonce++);
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}
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for (size_t i = 0; i < KYBER_K; i++) {
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PQCLEAN_KYBER76890S_CLEAN_poly_getnoise(e.vec + i, noiseseed, nonce++);
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}
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PQCLEAN_KYBER76890S_CLEAN_polyvec_ntt(&skpv);
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PQCLEAN_KYBER76890S_CLEAN_polyvec_ntt(&e);
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// matrix-vector multiplication
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for (size_t i = 0; i < KYBER_K; i++) {
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PQCLEAN_KYBER76890S_CLEAN_polyvec_pointwise_acc(&pkpv.vec[i], &a[i], &skpv);
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PQCLEAN_KYBER76890S_CLEAN_poly_frommont(&pkpv.vec[i]);
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}
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PQCLEAN_KYBER76890S_CLEAN_polyvec_add(&pkpv, &pkpv, &e);
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PQCLEAN_KYBER76890S_CLEAN_polyvec_reduce(&pkpv);
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pack_sk(sk, &skpv);
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pack_pk(pk, &pkpv, publicseed);
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}
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/*************************************************
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* Name: indcpa_enc
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*
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* Description: Encryption function of the CPA-secure
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* public-key encryption scheme underlying Kyber.
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*
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* Arguments: - uint8_t *c: pointer to output ciphertext (of length KYBER_INDCPA_BYTES bytes)
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* - const uint8_t *m: pointer to input message (of length KYBER_INDCPA_MSGBYTES bytes)
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* - const uint8_t *pk: pointer to input public key (of length KYBER_INDCPA_PUBLICKEYBYTES bytes)
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* - const uint8_t *coin: pointer to input random coins used as seed (of length KYBER_SYMBYTES bytes)
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* to deterministically generate all randomness
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**************************************************/
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void PQCLEAN_KYBER76890S_CLEAN_indcpa_enc(uint8_t *c,
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const uint8_t *m,
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const uint8_t *pk,
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const uint8_t *coins) {
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polyvec sp, pkpv, ep, at[KYBER_K], bp;
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poly v, k, epp;
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uint8_t seed[KYBER_SYMBYTES];
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uint8_t nonce = 0;
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unpack_pk(&pkpv, seed, pk);
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PQCLEAN_KYBER76890S_CLEAN_poly_frommsg(&k, m);
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gen_at(at, seed);
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for (size_t i = 0; i < KYBER_K; i++) {
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PQCLEAN_KYBER76890S_CLEAN_poly_getnoise(sp.vec + i, coins, nonce++);
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}
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for (size_t i = 0; i < KYBER_K; i++) {
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PQCLEAN_KYBER76890S_CLEAN_poly_getnoise(ep.vec + i, coins, nonce++);
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}
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PQCLEAN_KYBER76890S_CLEAN_poly_getnoise(&epp, coins, nonce++);
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PQCLEAN_KYBER76890S_CLEAN_polyvec_ntt(&sp);
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// matrix-vector multiplication
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for (size_t i = 0; i < KYBER_K; i++) {
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PQCLEAN_KYBER76890S_CLEAN_polyvec_pointwise_acc(&bp.vec[i], &at[i], &sp);
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}
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PQCLEAN_KYBER76890S_CLEAN_polyvec_pointwise_acc(&v, &pkpv, &sp);
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PQCLEAN_KYBER76890S_CLEAN_polyvec_invntt(&bp);
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PQCLEAN_KYBER76890S_CLEAN_poly_invntt(&v);
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PQCLEAN_KYBER76890S_CLEAN_polyvec_add(&bp, &bp, &ep);
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PQCLEAN_KYBER76890S_CLEAN_poly_add(&v, &v, &epp);
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PQCLEAN_KYBER76890S_CLEAN_poly_add(&v, &v, &k);
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PQCLEAN_KYBER76890S_CLEAN_polyvec_reduce(&bp);
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PQCLEAN_KYBER76890S_CLEAN_poly_reduce(&v);
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pack_ciphertext(c, &bp, &v);
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}
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/*************************************************
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* Name: indcpa_dec
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*
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* Description: Decryption function of the CPA-secure
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* public-key encryption scheme underlying Kyber.
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*
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* Arguments: - uint8_t *m: pointer to output decrypted message (of length KYBER_INDCPA_MSGBYTES)
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* - const uint8_t *c: pointer to input ciphertext (of length KYBER_INDCPA_BYTES)
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* - const uint8_t *sk: pointer to input secret key (of length KYBER_INDCPA_SECRETKEYBYTES)
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**************************************************/
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void PQCLEAN_KYBER76890S_CLEAN_indcpa_dec(uint8_t *m,
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const uint8_t *c,
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const uint8_t *sk) {
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polyvec bp, skpv;
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poly v, mp;
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unpack_ciphertext(&bp, &v, c);
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unpack_sk(&skpv, sk);
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PQCLEAN_KYBER76890S_CLEAN_polyvec_ntt(&bp);
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PQCLEAN_KYBER76890S_CLEAN_polyvec_pointwise_acc(&mp, &skpv, &bp);
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PQCLEAN_KYBER76890S_CLEAN_poly_invntt(&mp);
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PQCLEAN_KYBER76890S_CLEAN_poly_sub(&mp, &v, &mp);
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PQCLEAN_KYBER76890S_CLEAN_poly_reduce(&mp);
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PQCLEAN_KYBER76890S_CLEAN_poly_tomsg(m, &mp);
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}
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