OpenSSL CVS Repository
http://cvs.openssl.org/
____________________________________________________________________________
Server: cvs.openssl.org Name: Richard Levitte
Root: /e/openssl/cvs Email: levitte@xxxxxxxxxxx
Module: openssl Date: 03-Jul-2003 08:41:33
Branch: OpenSSL_0_9_7-stable Handle: 2003070307413300
Modified files: (Branch: OpenSSL_0_9_7-stable)
openssl/crypto/aes aes_ctr.c
Log:
Change AES-CTR to increment the IV by 1 instead of 2^64.
Summary:
Revision Changes Path
1.1.2.6 +43 -7 openssl/crypto/aes/aes_ctr.c
____________________________________________________________________________
patch -p0 <<'@@ .'
Index: openssl/crypto/aes/aes_ctr.c
============================================================================
$ cvs diff -u -r1.1.2.5 -r1.1.2.6 aes_ctr.c
--- openssl/crypto/aes/aes_ctr.c 13 Nov 2002 14:01:19 -0000 1.1.2.5
+++ openssl/crypto/aes/aes_ctr.c 3 Jul 2003 06:41:33 -0000 1.1.2.6
@@ -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 + 0, c);
+#else
+ c = GETU32(counter + 12);
+ 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);
+ PUTU32(counter + 8, c);
#else
- c = GETU32(counter + 4);
+ c = GETU32(counter + 4);
c++;
- PUTU32(counter + 4, c);
+ PUTU32(counter + 4, c);
#endif
/* if no overflow, we're done */
@@ -100,10 +130,16 @@
* 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) {
@@ .
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