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Change AES-CTR to increment the IV by 1 instead of 2^64.

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This commit is contained in:
Richard Levitte 2003-07-03 06:41:33 +00:00
parent ec28f9c12c
commit 29e62e487f
1 changed files with 43 additions and 7 deletions
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50
crypto/aes/aes_ctr.c
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@ -62,19 +62,49 @@
/* NOTE: CTR mode is big-endian. The rest of the AES code
* is endian-neutral. */
/* increment counter (128-bit int) by 2^64 */
/* increment counter (128-bit int) by 1 */
static void AES_ctr128_inc(unsigned char *counter) {
unsigned long c;
/* Grab 3rd dword of counter and increment */
/* Grab bottom dword of counter and increment */
#ifdef L_ENDIAN
c = GETU32(counter + 8);
c = GETU32(counter + 0);
c++;
PUTU32(counter + 8, c);
PUTU32(counter + 0, c);
#else
c = GETU32(counter + 4);
c = GETU32(counter + 12);
c++;
PUTU32(counter + 4, c);
PUTU32(counter + 12, c);
#endif
/* if no overflow, we're done */
if (c)
return;
/* Grab 1st dword of counter and increment */
#ifdef L_ENDIAN
c = GETU32(counter + 4);
c++;
PUTU32(counter + 4, c);
#else
c = GETU32(counter + 8);
c++;
PUTU32(counter + 8, c);
#endif
/* if no overflow, we're done */
if (c)
return;
/* Grab 2nd dword of counter and increment */
#ifdef L_ENDIAN
c = GETU32(counter + 8);
c++;
PUTU32(counter + 8, c);
#else
c = GETU32(counter + 4);
c++;
PUTU32(counter + 4, c);
#endif
/* if no overflow, we're done */
@ -100,10 +130,16 @@ static void AES_ctr128_inc(unsigned char *counter) {
* encrypted counter is kept in ecount_buf. Both *num and
* ecount_buf must be initialised with zeros before the first
* call to AES_ctr128_encrypt().
*
* This algorithm assumes that the counter is in the x lower bits
* of the IV (ivec), and that the application has full control over
* overflow and the rest of the IV. This implementation takes NO
* responsability for checking that the counter doesn't overflow
* into the rest of the IV when incremented.
*/
void AES_ctr128_encrypt(const unsigned char *in, unsigned char *out,
const unsigned long length, const AES_KEY *key,
unsigned char counter[AES_BLOCK_SIZE],
unsigned char ivec[AES_BLOCK_SIZE],
unsigned char ecount_buf[AES_BLOCK_SIZE],
unsigned int *num) {