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/*
* cifra - embedded cryptography library
* Written in 2014 by Joseph Birr-Pixton <jpixton@gmail.com>
*
* To the extent possible under law, the author(s) have dedicated all
* copyright and related and neighboring rights to this software to the
* public domain worldwide. This software is distributed without any
* warranty.
*
* You should have received a copy of the CC0 Public Domain Dedication
* along with this software. If not, see
* <http://creativecommons.org/publicdomain/zero/1.0/>.
*/
/**
* The AES block cipher
* ====================
*
* This is a small, simple implementation of AES. Key expansion is done
* first, filling in a :c:type:`cf_aes_context`. Then encryption and
* decryption can be performed as desired.
*
* Usually you don't want to use AES directly; you should use it via
* a :doc:`block cipher mode <modes>`.
*/
#ifndef AES_H
#define AES_H
#include <stddef.h>
#include <stdint.h>
#include "prp.h"
/* .. c:macro:: AES_BLOCKSZ
* AES has a 128-bit block size. This quantity is in bytes.
*/
#define AES_BLOCKSZ 16
/* --- Size configuration --- */
/* .. c:macro:: AES128_ROUNDS
* .. c:macro:: AES192_ROUNDS
* .. c:macro:: AES256_ROUNDS
*
* Round counts for different key sizes.
*/
#define AES128_ROUNDS 10
#define AES192_ROUNDS 12
#define AES256_ROUNDS 14
/* .. c:macro:: CF_AES_MAXROUNDS
*
* You can reduce the maximum number of rounds this implementation
* supports. This reduces the storage needed by :c:type:`cf_aes_context`.
*
* The default is :c:macro:`AES256_ROUNDS` and is good for all key
* sizes.
*/
#ifndef CF_AES_MAXROUNDS
# define CF_AES_MAXROUNDS AES256_ROUNDS
#endif
/* .. c:macro:: CF_AES_ENCRYPT_ONLY
*
* Define this to 1 if you don't need to decrypt anything.
* This saves space. :c:func:`cf_aes_decrypt` calls `abort(3)`.
*/
#ifndef CF_AES_ENCRYPT_ONLY
# define CF_AES_ENCRYPT_ONLY 0
#endif
/* .. c:type:: cf_aes_context
* This type represents an expanded AES key. Create one
* using :c:func:`cf_aes_init`, make use of one using
* :c:func:`cf_aes_encrypt` or :c:func:`cf_aes_decrypt`.
*
* The contents of this structure are equivalent to the
* original key material. You should clean the
* contents of this structure with :c:func:`cf_aes_finish`
* when you're done.
*
* .. c:member:: cf_aes_context.rounds
*
* Number of rounds to use, set by :c:func:`cf_aes_init`.
*
* This depends on the original key size, and will be
* :c:macro:`AES128_ROUNDS`, :c:macro:`AES192_ROUNDS` or
* :c:macro:`AES256_ROUNDS`.
*
* .. c:member:: cf_aes_context.ks
*
* Expanded key material. Filled in by :c:func:`cf_aes_init`.
*/
typedef struct
{
uint32_t rounds;
uint32_t ks[AES_BLOCKSZ / 4 * (CF_AES_MAXROUNDS + 1)];
} cf_aes_context;
/* .. c:function:: $DECL
* This function does AES key expansion. It destroys
* existing contents of :c:data:`ctx`.
*
* :param ctx: expanded key context, filled in by this function.
* :param key: pointer to key material, of :c:data:`nkey` bytes.
* :param nkey: length of key material. Must be `16`, `24` or `32`.
*/
extern void cf_aes_init(cf_aes_context *ctx,
const uint8_t *key,
size_t nkey);
/* .. c:function:: $DECL
* Encrypts the given block, from :c:data:`in` to :c:data:`out`.
* These may alias.
*
* Fails at runtime if :c:data:`ctx` is invalid.
*
* :param ctx: expanded key context
* :param in: input block (read)
* :param out: output block (written)
*/
extern void cf_aes_encrypt(const cf_aes_context *ctx,
const uint8_t in[AES_BLOCKSZ],
uint8_t out[AES_BLOCKSZ]);
/* .. c:function:: $DECL
* Decrypts the given block, from :c:data:`in` to :c:data:`out`.
* These may alias.
*
* Fails at runtime if :c:data:`ctx` is invalid.
*
* :param ctx: expanded key context
* :param in: input block (read)
* :param out: output block (written)
*/
extern void cf_aes_decrypt(const cf_aes_context *ctx,
const uint8_t in[AES_BLOCKSZ],
uint8_t out[AES_BLOCKSZ]);
/* .. c:function:: $DECL
* Erase scheduled key material.
*
* Call this when you're done to erase the round keys. */
extern void cf_aes_finish(cf_aes_context *ctx);
/* .. c:var:: const cf_prp cf_aes
* Abstract interface to AES. See :c:type:`cf_prp` for
* more information. */
extern const cf_prp cf_aes;
#endif
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