120 lines
3.0 KiB
C
120 lines
3.0 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_encrypt.c
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CFB implementation, encrypt data, Tom St Denis
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*/
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#ifdef LTC_CFB_MODE
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#ifndef LTC_CFB_SHIFT1LEFT
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#define LTC_CFB_SHIFT1LEFT
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static LTC_INLINE void s_shift1left_64(unsigned char *b, unsigned char v)
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{
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ulong64 bval;
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LOAD64H(bval, b);
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bval <<= 1;
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bval |= v & 0x01u;
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STORE64H(bval, b);
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}
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static LTC_INLINE void s_shift1left_128(unsigned char *b, unsigned char v)
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{
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ulong64 bval[2];
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LOAD64H(bval[0], b);
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LOAD64H(bval[1], b + 8);
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bval[0] <<= 1;
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bval[0] |= (bval[1] >> 63) & 0x01u;
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bval[1] <<= 1;
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bval[1] |= v & 0x01u;
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STORE64H(bval[0], b);
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STORE64H(bval[1], b + 8);
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}
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#endif /* LTC_CFB_SHIFT1LEFT */
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/**
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CFB encrypt
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@param pt Plaintext
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@param ct [out] Ciphertext
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@param len Length of plaintext (octets)
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@param cfb CFB state
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@return CRYPT_OK if successful
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*/
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int cfb_encrypt(const unsigned char *pt, unsigned char *ct, unsigned long len, symmetric_CFB *cfb)
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{
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int err;
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ulong64 bitlen = len * 8, bits_per_round;
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unsigned int cur_bit = 0;
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unsigned char pt_ = 0, ct_ = 0;
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LTC_ARGCHK(pt != NULL);
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LTC_ARGCHK(ct != NULL);
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LTC_ARGCHK(cfb != NULL);
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if (bitlen < len) {
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return CRYPT_OVERFLOW;
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}
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if ((err = cipher_is_valid(cfb->ecb.cipher)) != CRYPT_OK) {
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return err;
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}
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/* is blocklen/padlen valid? */
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if (cfb->ecb.blocklen < 0 || cfb->ecb.blocklen > (int)sizeof(cfb->IV) ||
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cfb->padlen < 0 || cfb->padlen > (int)sizeof(cfb->pad)) {
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return CRYPT_INVALID_ARG;
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}
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bits_per_round = cfb->width == 1 ? 1 : 8;
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while (bitlen > 0) {
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if (cfb->padlen == cfb->ecb.blocklen) {
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if ((err = ecb_encrypt_block(cfb->pad, cfb->IV, &cfb->ecb)) != CRYPT_OK) {
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return err;
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}
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cfb->padlen = 0;
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}
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switch (cfb->width) {
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case 1:
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if (cur_bit++ % 8 == 0) {
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pt_ = *pt++;
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ct_ = 0;
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} else {
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pt_ <<= 1;
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ct_ <<= 1;
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}
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ct_ |= ((pt_ ^ cfb->IV[0]) >> 7) & 0x01u;
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if (cfb->ecb.blocklen == 16)
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s_shift1left_128(cfb->pad, ct_);
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else
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s_shift1left_64(cfb->pad, ct_);
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cfb->padlen = cfb->ecb.blocklen;
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if (cur_bit % 8 == 0) {
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*ct++ = ct_;
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cur_bit = 0;
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}
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break;
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case 8:
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XMEMMOVE(cfb->pad, cfb->pad + 1, cfb->ecb.blocklen - 1);
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cfb->pad[cfb->ecb.blocklen - 1] = (*ct = *pt ^ cfb->IV[0]);
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++pt;
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++ct;
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cfb->padlen = cfb->ecb.blocklen;
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break;
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case 64:
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case 128:
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cfb->pad[cfb->padlen] = (*ct = *pt ^ cfb->IV[cfb->padlen]);
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++pt;
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++ct;
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++(cfb->padlen);
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break;
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}
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bitlen -= bits_per_round;
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}
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return CRYPT_OK;
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}
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#endif
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