lc_ascon_aead.h

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/*
 * Copyright (C) 2024 - 2025, Stephan Mueller <smueller@chronox.de>
 *
 * License: see LICENSE file in root directory
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE, ALL OF
 * WHICH ARE HEREBY DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
 * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
 * BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE
 * USE OF THIS SOFTWARE, EVEN IF NOT ADVISED OF THE POSSIBILITY OF SUCH
 * DAMAGE.
 */
 
#ifndef LC_ASCON_AEAD_H
#define LC_ASCON_AEAD_H
 
#include "lc_aead.h"
#include "lc_hash.h"
 
#ifdef __cplusplus
extern "C" {
#endif

#define LC_ASCON_MAX_KEYSIZE 64
 
struct lc_ascon_cryptor {
        uint8_t key[LC_ASCON_MAX_KEYSIZE];
        uint8_t keylen;
        uint8_t rate_offset;
        uint8_t statesize;
        uint8_t roundb;
        uint8_t taglen;
        const struct lc_hash *hash;
        uint64_t *state;
};
 
#define LC_ASCON_ALIGNMENT LC_XOR_ALIGNMENT(LC_HASH_COMMON_ALIGNMENT)
 
#define _LC_ASCON_SET_CTX(name, hashname, ctx, offset)                         \
        name->state = LC_ALIGN_HASH_MASK(((uint8_t *)(ctx)) + (offset));       \
        name->hash = hashname
 
#define LC_ASCON_SET_CTX(name, hashname, ascon_impl)                           \
        LC_AEAD_HASH_ALIGN_CTX(name, ascon_impl);                              \
        _LC_ASCON_SET_CTX(((struct lc_ascon_cryptor *)name->aead_state),       \
                          hashname,                                            \
                          ((struct lc_ascon_cryptor *)name->aead_state),       \
                          (sizeof(struct lc_ascon_cryptor)))
 
static inline int lc_ascon_load_key(struct lc_ascon_cryptor *ascon,
                                    const uint8_t *key, size_t keylen)
{
        if (ascon && keylen < LC_ASCON_MAX_KEYSIZE) {
                memcpy(ascon->key, key, keylen);
                ascon->keylen = (uint8_t)keylen;
                return 0;
        }
        return -EINVAL;
}
 
/*
 * This function adds the padding byte with which the AAD as well as the
 * plaintext is appended with.
 */
static inline void lc_ascon_add_padbyte(struct lc_ascon_cryptor *ascon,
                                        size_t offset)
{
        const struct lc_hash *hash = ascon->hash;
        /* Rationale for pad byte: see ascon_squeeze_common */
        static const uint8_t pad_data = 0x01;
 
        /*
         * The data was exactly a multiple of the rate -> permute before adding
         * the padding byte.
         */
        if (offset == hash->sponge_rate)
                offset = 0;
 
        lc_sponge_add_bytes(hash, ascon->state, &pad_data, offset, 1);
}
 
#ifdef __cplusplus
}
#endif
 
#endif /* LC_ASCON_AEAD_H */