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des: add possibility to calculate DES-CBC-MAC with small buffer

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This patch adds the possibility to calculate the DES-CBC-MAC of a
source buffer (i.e. the last block of the buffer encrypted in CBC
mode) without having to allocate a destination buffer that is as
long as the complete source buffer, but instead only 8 bytes
for the MAC.

Signed-off-by: David Goldwich <david.goldwich@gmail.com>
Signed-off-by: Anton Khirnov <anton@khirnov.net>
This commit is contained in:
David Goldwich 2011-09-02 08:20:58 +02:00 committed by Anton Khirnov
parent 3ffe32eb96
commit b3e144a7df
2 changed files with 21 additions and 3 deletions
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13
libavutil/des.c
View File

@ -298,7 +298,7 @@ int av_des_init(AVDES *d, const uint8_t *key, int key_bits, int decrypt) {
return 0;
}
void av_des_crypt(AVDES *d, uint8_t *dst, const uint8_t *src, int count, uint8_t *iv, int decrypt) {
static void av_des_crypt_mac(AVDES *d, uint8_t *dst, const uint8_t *src, int count, uint8_t *iv, int decrypt, int mac) {
uint64_t iv_val = iv ? AV_RB64(iv) : 0;
while (count-- > 0) {
uint64_t dst_val;
@ -321,12 +321,21 @@ void av_des_crypt(AVDES *d, uint8_t *dst, const uint8_t *src, int count, uint8_t
}
AV_WB64(dst, dst_val);
src += 8;
dst += 8;
if (!mac)
dst += 8;
}
if (iv)
AV_WB64(iv, iv_val);
}
void av_des_crypt(AVDES *d, uint8_t *dst, const uint8_t *src, int count, uint8_t *iv, int decrypt) {
av_des_crypt_mac(d, dst, src, count, iv, decrypt, 0);
}
void av_des_mac(AVDES *d, uint8_t *dst, const uint8_t *src, int count) {
av_des_crypt_mac(d, dst, src, count, (uint8_t[8]){0}, 0, 1);
}
#ifdef TEST
#undef printf
#undef rand

11
libavutil/des.h
View File

@ -33,7 +33,7 @@ struct AVDES {
* @brief Initializes an AVDES context.
*
* @param key_bits must be 64 or 192
* @param decrypt 0 for encryption, 1 for decryption
* @param decrypt 0 for encryption/CBC-MAC, 1 for decryption
*/
int av_des_init(struct AVDES *d, const uint8_t *key, int key_bits, int decrypt);
@ -49,4 +49,13 @@ int av_des_init(struct AVDES *d, const uint8_t *key, int key_bits, int decrypt);
*/
void av_des_crypt(struct AVDES *d, uint8_t *dst, const uint8_t *src, int count, uint8_t *iv, int decrypt);
/**
* @brief Calculates CBC-MAC using the DES algorithm.
*
* @param count number of 8 byte blocks
* @param dst destination array, can be equal to src, must be 8-byte aligned
* @param src source array, can be equal to dst, must be 8-byte aligned, may be NULL
*/
void av_des_mac(struct AVDES *d, uint8_t *dst, const uint8_t *src, int count);
#endif /* AVUTIL_DES_H */