87 lines
2.4 KiB
C
87 lines
2.4 KiB
C
/* LibTomCrypt, modular cryptographic library -- Tom St Denis */
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/* SPDX-License-Identifier: Unlicense */
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#include "tomcrypt_private.h"
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/**
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@file cfb_start.c
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CFB implementation, start chain, Tom St Denis
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*/
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#ifdef LTC_CFB_MODE
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/**
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Extended initialization of a CFB context
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@param cipher The index of the cipher desired
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@param IV The initialization vector
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@param key The secret key
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@param keylen The length of the secret key (octets)
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@param num_rounds Number of rounds in the cipher desired (0 for default)
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@param width The width of the mode in bits (0 for default)
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@param cfb The CFB state to initialize
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@return CRYPT_OK if successful
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*/
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int cfb_start_ex(int cipher, const unsigned char *IV, const unsigned char *key,
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int keylen, int num_rounds, int width, symmetric_CFB *cfb)
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{
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int x, err;
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LTC_ARGCHK(IV != NULL);
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LTC_ARGCHK(key != NULL);
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LTC_ARGCHK(cfb != NULL);
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if ((err = cipher_is_valid(cipher)) != CRYPT_OK) {
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return err;
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}
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switch (width) {
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case 0:
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width = cipher_descriptor[cipher].block_length * 8;
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break;
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case 1:
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case 8:
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LTC_ARGCHK(cipher_descriptor[cipher].block_length == 8
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|| cipher_descriptor[cipher].block_length == 16);
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break;
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case 64:
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case 128:
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LTC_ARGCHK(width == cipher_descriptor[cipher].block_length * 8);
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break;
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default:
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return CRYPT_INVALID_ARG;
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}
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cfb->width = width;
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/* init the cipher */
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if ((err = ecb_start(cipher, key, keylen, num_rounds, &cfb->ecb)) != CRYPT_OK) {
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return err;
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}
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/* copy data */
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for (x = 0; x < cfb->ecb.blocklen; x++) {
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cfb->pad[x] = IV[x];
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}
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/* encrypt the IV */
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cfb->padlen = 0;
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return ecb_encrypt_block(cfb->pad, cfb->IV, &cfb->ecb);
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}
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/**
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Initialize a CFB context
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@param cipher The index of the cipher desired
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@param IV The initialization vector
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@param key The secret key
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@param keylen The length of the secret key (octets)
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@param num_rounds Number of rounds in the cipher desired (0 for default)
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@param cfb The CFB state to initialize
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@return CRYPT_OK if successful
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*/
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int cfb_start(int cipher, const unsigned char *IV, const unsigned char *key,
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int keylen, int num_rounds, symmetric_CFB *cfb)
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{
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return cfb_start_ex(cipher, IV, key, keylen, num_rounds, 0, cfb);
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}
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#endif
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