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/* LibTomCrypt, modular cryptographic library -- Tom St Denis
*
* LibTomCrypt is a library that provides various cryptographic
* algorithms in a highly modular and flexible manner.
*
* The library is free for all purposes without any express
* guarantee it works.
*/
#include "tomcrypt.h"
#if defined(LTC_MECC) && defined(LTC_DER)
/**
@file ecc_sign_hash.c
ECC Crypto, Tom St Denis
*/
static int _ecc_sign_hash(const unsigned char *in, unsigned long inlen,
unsigned char *out, unsigned long *outlen,
prng_state *prng, int wprng, ecc_key *key, int sigformat)
{
ecc_key pubkey;
void *r, *s, *e, *p, *b;
int err, max_iterations = LTC_PK_MAX_RETRIES;
unsigned long pbits, pbytes, i, shift_right;
unsigned char ch, buf[MAXBLOCKSIZE];
LTC_ARGCHK(in != NULL);
LTC_ARGCHK(out != NULL);
LTC_ARGCHK(outlen != NULL);
LTC_ARGCHK(key != NULL);
/* is this a private key? */
if (key->type != PK_PRIVATE) {
return CRYPT_PK_NOT_PRIVATE;
}
/* is the IDX valid ? */
if (ltc_ecc_is_valid_idx(key->idx) != 1) {
return CRYPT_PK_INVALID_TYPE;
}
if ((err = prng_is_valid(wprng)) != CRYPT_OK) {
return err;
}
/* init the bignums */
if ((err = mp_init_multi(&r, &s, &p, &e, &b, NULL)) != CRYPT_OK) {
return err;
}
if ((err = mp_read_radix(p, (char *)key->dp->order, 16)) != CRYPT_OK) { goto errnokey; }
/* get the hash and load it as a bignum into 'e' */
pbits = mp_count_bits(p);
pbytes = (pbits+7) >> 3;
if (pbits > inlen*8) {
if ((err = mp_read_unsigned_bin(e, (unsigned char *)in, inlen)) != CRYPT_OK) { goto errnokey; }
}
else if (pbits % 8 == 0) {
if ((err = mp_read_unsigned_bin(e, (unsigned char *)in, pbytes)) != CRYPT_OK) { goto errnokey; }
}
else {
shift_right = 8 - pbits % 8;
for (i=0, ch=0; i<pbytes; i++) {
buf[i] = ch;
ch = (in[i] << (8-shift_right));
buf[i] = buf[i] ^ (in[i] >> shift_right);
}
if ((err = mp_read_unsigned_bin(e, (unsigned char *)buf, pbytes)) != CRYPT_OK) { goto errnokey; }
}
/* make up a key and export the public copy */
do {
if ((err = ecc_make_key_ex(prng, wprng, &pubkey, key->dp)) != CRYPT_OK) {
goto errnokey;
}
/* find r = x1 mod n */
if ((err = mp_mod(pubkey.pubkey.x, p, r)) != CRYPT_OK) { goto error; }
if (mp_iszero(r) == LTC_MP_YES) {
ecc_free(&pubkey);
} else {
if ((err = rand_bn_upto(b, p, prng, wprng)) != CRYPT_OK) { goto error; } /* b = blinding value */
/* find s = (e + xr)/k */
if ((err = mp_mulmod(pubkey.k, b, p, pubkey.k)) != CRYPT_OK) { goto error; } /* k = kb */
if ((err = mp_invmod(pubkey.k, p, pubkey.k)) != CRYPT_OK) { goto error; } /* k = 1/kb */
if ((err = mp_mulmod(key->k, r, p, s)) != CRYPT_OK) { goto error; } /* s = xr */
if ((err = mp_mulmod(pubkey.k, s, p, s)) != CRYPT_OK) { goto error; } /* s = xr/kb */
if ((err = mp_mulmod(pubkey.k, e, p, e)) != CRYPT_OK) { goto error; } /* e = e/kb */
if ((err = mp_add(e, s, s)) != CRYPT_OK) { goto error; } /* s = e/kb + xr/kb */
if ((err = mp_mulmod(s, b, p, s)) != CRYPT_OK) { goto error; } /* s = b(e/kb + xr/kb) = (e + xr)/k */
ecc_free(&pubkey);
if (mp_iszero(s) == LTC_MP_NO) {
break;
}
}
} while (--max_iterations > 0);
if (max_iterations == 0) {
goto errnokey;
}
if (sigformat == 1) {
/* RFC7518 format */
if (*outlen < 2*pbytes) { err = CRYPT_MEM; goto errnokey; }
zeromem(out, 2*pbytes);
i = mp_unsigned_bin_size(r);
if ((err = mp_to_unsigned_bin(r, out + (pbytes - i))) != CRYPT_OK) { goto errnokey; }
i = mp_unsigned_bin_size(s);
if ((err = mp_to_unsigned_bin(s, out + (2*pbytes - i))) != CRYPT_OK) { goto errnokey; }
*outlen = 2*pbytes;
err = CRYPT_OK;
}
else {
/* store as ASN.1 SEQUENCE { r, s -- integer } */
err = der_encode_sequence_multi(out, outlen,
LTC_ASN1_INTEGER, 1UL, r,
LTC_ASN1_INTEGER, 1UL, s,
LTC_ASN1_EOL, 0UL, NULL);
}
goto errnokey;
error:
ecc_free(&pubkey);
errnokey:
mp_clear_multi(r, s, p, e, b, NULL);
return err;
}
/**
Sign a message digest
@param in The message digest to sign
@param inlen The length of the digest
@param out [out] The destination for the signature
@param outlen [in/out] The max size and resulting size of the signature
@param prng An active PRNG state
@param wprng The index of the PRNG you wish to use
@param key A private ECC key
@return CRYPT_OK if successful
*/
int ecc_sign_hash(const unsigned char *in, unsigned long inlen,
unsigned char *out, unsigned long *outlen,
prng_state *prng, int wprng, ecc_key *key)
{
return _ecc_sign_hash(in, inlen, out, outlen, prng, wprng, key, 0);
}
/**
Sign a message digest in RFC7518 format
@param in The message digest to sign
@param inlen The length of the digest
@param out [out] The destination for the signature
@param outlen [in/out] The max size and resulting size of the signature
@param prng An active PRNG state
@param wprng The index of the PRNG you wish to use
@param key A private ECC key
@return CRYPT_OK if successful
*/
int ecc_sign_hash_rfc7518(const unsigned char *in, unsigned long inlen,
unsigned char *out, unsigned long *outlen,
prng_state *prng, int wprng, ecc_key *key)
{
return _ecc_sign_hash(in, inlen, out, outlen, prng, wprng, key, 1);
}
#endif
/* ref: $Format:%D$ */
/* git commit: $Format:%H$ */
/* commit time: $Format:%ai$ */
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