generic-library/openssl
1
0
Fork 0
Code Issues Pull Requests Releases Wiki Activity

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

Browse Source
This commit is contained in:
Richard Levitte 2003-07-03 06:41:30 +00:00
parent 9d19fbc4fc
commit da0d33560f
1 changed files with 43 additions and 7 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

50
crypto/aes/aes_ctr.c
View File

@ -62,19 +62,49 @@
/* NOTE: CTR mode is big-endian. The rest of the AES code /* NOTE: CTR mode is big-endian. The rest of the AES code
* is endian-neutral. */ * 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) { static void AES_ctr128_inc(unsigned char *counter) {
unsigned long c; unsigned long c;
/* Grab 3rd dword of counter and increment */ /* Grab bottom dword of counter and increment */
#ifdef L_ENDIAN #ifdef L_ENDIAN
c = GETU32(counter + 8); c = GETU32(counter + 0);
c++; c++;
PUTU32(counter + 8, c); PUTU32(counter + 0, c);
#else #else
c = GETU32(counter + 4); c = GETU32(counter + 12);
c++; 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 #endif
/* if no overflow, we're done */ /* 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 * encrypted counter is kept in ecount_buf. Both *num and
* ecount_buf must be initialised with zeros before the first * ecount_buf must be initialised with zeros before the first
* call to AES_ctr128_encrypt(). * 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, void AES_ctr128_encrypt(const unsigned char *in, unsigned char *out,
const unsigned long length, const AES_KEY *key, 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 char ecount_buf[AES_BLOCK_SIZE],
unsigned int *num) { unsigned int *num) {