mirror of
https://github.com/henrydcase/pqc.git
synced 2024-11-27 09:51:30 +00:00
121 lines
4.6 KiB
C
121 lines
4.6 KiB
C
#include "api.h"
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#include "fips202.h"
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#include "indcpa.h"
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#include "params.h"
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#include "randombytes.h"
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#include "verify.h"
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/*************************************************
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* Name: crypto_kem_keypair
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*
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* Description: Generates public and private key
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* for CCA-secure Kyber key encapsulation mechanism
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*
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* Arguments: - unsigned char *pk: pointer to output public key (an already
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*allocated array of CRYPTO_PUBLICKEYBYTES bytes)
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* - unsigned char *sk: pointer to output private key (an already
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*allocated array of CRYPTO_SECRETKEYBYTES bytes)
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*
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* Returns 0 (success)
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**************************************************/
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int crypto_kem_keypair(unsigned char *pk, unsigned char *sk) {
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size_t i;
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indcpa_keypair(pk, sk);
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for (i = 0; i < KYBER_INDCPA_PUBLICKEYBYTES; i++)
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sk[i + KYBER_INDCPA_SECRETKEYBYTES] = pk[i];
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sha3_256(sk + KYBER_SECRETKEYBYTES - 2 * KYBER_SYMBYTES, pk,
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KYBER_PUBLICKEYBYTES);
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randombytes(sk + KYBER_SECRETKEYBYTES - KYBER_SYMBYTES,
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KYBER_SYMBYTES); /* Value z for pseudo-random output on reject */
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return 0;
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}
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/*************************************************
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* Name: crypto_kem_enc
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*
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* Description: Generates cipher text and shared
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* secret for given public key
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*
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* Arguments: - unsigned char *ct: pointer to output cipher text (an
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*already allocated array of CRYPTO_CIPHERTEXTBYTES bytes)
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* - unsigned char *ss: pointer to output shared secret (an
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*already allocated array of CRYPTO_BYTES bytes)
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* - const unsigned char *pk: pointer to input public key (an
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*already allocated array of CRYPTO_PUBLICKEYBYTES bytes)
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*
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* Returns 0 (success)
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**************************************************/
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int crypto_kem_enc(unsigned char *ct, unsigned char *ss,
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const unsigned char *pk) {
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unsigned char kr[2 * KYBER_SYMBYTES]; /* Will contain key, coins */
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unsigned char buf[2 * KYBER_SYMBYTES];
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randombytes(buf, KYBER_SYMBYTES);
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sha3_256(buf, buf, KYBER_SYMBYTES); /* Don't release system RNG output */
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sha3_256(buf + KYBER_SYMBYTES, pk,
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KYBER_PUBLICKEYBYTES); /* Multitarget countermeasure for coins +
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contributory KEM */
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sha3_512(kr, buf, 2 * KYBER_SYMBYTES);
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indcpa_enc(ct, buf, pk,
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kr + KYBER_SYMBYTES); /* coins are in kr+KYBER_SYMBYTES */
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sha3_256(kr + KYBER_SYMBYTES, ct,
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KYBER_CIPHERTEXTBYTES); /* overwrite coins in kr with H(c) */
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sha3_256(ss, kr,
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2 * KYBER_SYMBYTES); /* hash concatenation of pre-k and H(c) to k */
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return 0;
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}
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/*************************************************
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* Name: crypto_kem_dec
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*
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* Description: Generates shared secret for given
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* cipher text and private key
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*
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* Arguments: - unsigned char *ss: pointer to output shared secret (an
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*already allocated array of CRYPTO_BYTES bytes)
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* - const unsigned char *ct: pointer to input cipher text (an
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*already allocated array of CRYPTO_CIPHERTEXTBYTES bytes)
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* - const unsigned char *sk: pointer to input private key (an
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*already allocated array of CRYPTO_SECRETKEYBYTES bytes)
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*
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* Returns 0.
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*
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* On failure, ss will contain a pseudo-random value.
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**************************************************/
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int crypto_kem_dec(unsigned char *ss, const unsigned char *ct,
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const unsigned char *sk) {
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size_t i;
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int fail;
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unsigned char cmp[KYBER_CIPHERTEXTBYTES];
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unsigned char buf[2 * KYBER_SYMBYTES];
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unsigned char kr[2 * KYBER_SYMBYTES]; /* Will contain key, coins, qrom-hash */
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const unsigned char *pk = sk + KYBER_INDCPA_SECRETKEYBYTES;
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indcpa_dec(buf, ct, sk);
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for (i = 0; i < KYBER_SYMBYTES;
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i++) /* Multitarget countermeasure for coins + contributory KEM */
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buf[KYBER_SYMBYTES + i] = sk[KYBER_SECRETKEYBYTES - 2 * KYBER_SYMBYTES +
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i]; /* Save hash by storing H(pk) in sk */
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sha3_512(kr, buf, 2 * KYBER_SYMBYTES);
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indcpa_enc(cmp, buf, pk,
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kr + KYBER_SYMBYTES); /* coins are in kr+KYBER_SYMBYTES */
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fail = verify(ct, cmp, KYBER_CIPHERTEXTBYTES);
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sha3_256(kr + KYBER_SYMBYTES, ct,
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KYBER_CIPHERTEXTBYTES); /* overwrite coins in kr with H(c) */
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cmov(kr, sk + KYBER_SECRETKEYBYTES - KYBER_SYMBYTES, KYBER_SYMBYTES,
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fail); /* Overwrite pre-k with z on re-encryption failure */
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sha3_256(ss, kr,
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2 * KYBER_SYMBYTES); /* hash concatenation of pre-k and H(c) to k */
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return 0;
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}
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