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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/>.
*/
#ifndef BLOCKWISE_H
#define BLOCKWISE_H
#include <stdint.h>
#include <stddef.h>
/* Processing function for cf_blockwise_accumulate. */
typedef void (*cf_blockwise_in_fn)(void *ctx, const uint8_t *data);
/* Processing function for cf_blockwise_xor. */
typedef void (*cf_blockwise_out_fn)(void *ctx, uint8_t *data);
/* This function manages the common abstraction of accumulating input in
* a buffer, and processing it when a full block is available.
*
* partial is the buffer (maintained by the caller)
* on entry, npartial is the currently valid count of used bytes on
* the front of partial.
* on exit, npartial is updated to reflect the status of partial.
* nblock is the blocksize to accumulate -- partial must be at least
* this long!
* input is the new data to process, of length nbytes.
* process is the processing function, passed ctx and a pointer
* to the data to process (always exactly nblock bytes long!)
* which may not neccessarily be the same as partial.
*/
void cf_blockwise_accumulate(uint8_t *partial, size_t *npartial,
size_t nblock,
const void *input, size_t nbytes,
cf_blockwise_in_fn process,
void *ctx);
/* This function manages the common abstraction of accumulating input in
* a buffer, and processing it when a full block is available.
* This version supports calling a different processing function for
* the last block.
*
* partial is the buffer (maintained by the caller)
* on entry, npartial is the currently valid count of used bytes on
* the front of partial.
* on exit, npartial is updated to reflect the status of partial.
* nblock is the blocksize to accumulate -- partial must be at least
* this long!
* input is the new data to process, of length nbytes.
* process is the processing function, passed ctx and a pointer
* to the data to process (always exactly nblock bytes long!)
* which may not neccessarily be the same as partial.
* process_final is called last (but may not be called at all if
* all input is buffered).
*/
void cf_blockwise_accumulate_final(uint8_t *partial, size_t *npartial,
size_t nblock,
const void *input, size_t nbytes,
cf_blockwise_in_fn process,
cf_blockwise_in_fn process_final,
void *ctx);
/* This function manages XORing an input stream with a keystream
* to produce an output stream. The keystream is produced in blocks
* (ala a block cipher in counter mode).
*
* partial is the keystream buffer (maintained by the caller)
* on entry, *npartial is the currently valid count of bytes in partial:
* unused bytes are at the *end*. So *npartial = 4 means the last four
* bytes of partial are usable as keystream.
* on exit, npartial is updated to reflect the new state of partial.
* nblock is the blocksize to accumulate -- partial must be at least
* this long!
* input is the new data to process, of length nbytes.
* output is where to write input xored with the keystream -- also length
* nbytes.
* process is the processing function, passed ctx and partial which it
* should fill with fresh key stream.
*/
void cf_blockwise_xor(uint8_t *partial, size_t *npartial,
size_t nblock,
const void *input, void *output, size_t nbytes,
cf_blockwise_out_fn newblock,
void *ctx);
/* This function processes a single byte a number of times. It's useful
* for padding, and more efficient than calling cf_blockwise_accumulate
* a bunch of times.
*
* partial is the buffer (maintained by the caller)
* on entry, npartial is the currently valid count of used bytes on
* the front of partial.
* on exit, npartial is updated to reflect the status of partial.
* nblock is the blocksize to accumulate -- partial must be at least
* this long!
* process is the processing function, passed ctx and a pointer
* to the data to process (always exactly nblock bytes long!)
* which may not neccessarily be the same as partial.
* byte is the byte to process, nbytes times.
*/
void cf_blockwise_acc_byte(uint8_t *partial, size_t *npartial,
size_t nblock,
uint8_t byte, size_t nbytes,
cf_blockwise_in_fn process,
void *ctx);
/* This function attempts to process patterns of bytes common in
* block cipher padding.
*
* This takes three bytes:
* - a first byte, fbyte,
* - a middle byte, mbyte,
* - a last byte, lbyte.
*
* If nbytes is zero, nothing happens.
* If nbytes is one, the byte fbyte ^ lbyte is processed.
* If nbytes is two, the fbyte then lbyte are processed.
* If nbytes is three or more, fbyte, then one or more mbytes, then fbyte
* is processed.
*
* partial is the buffer (maintained by the caller)
* on entry, npartial is the currently valid count of used bytes on
* the front of partial.
* on exit, npartial is updated to reflect the status of partial.
* nblock is the blocksize to accumulate -- partial must be at least
* this long!
* process is the processing function, passed ctx and a pointer
* to the data to process (always exactly nblock bytes long!)
* which may not neccessarily be the same as partial.
*/
void cf_blockwise_acc_pad(uint8_t *partial, size_t *npartial,
size_t nblock,
uint8_t fbyte, uint8_t mbyte, uint8_t lbyte,
size_t nbytes,
cf_blockwise_in_fn process,
void *ctx);
#endif
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