commit 46697da5b3b555148c7e5a46aaf70393c6a48eb3
author Dave Rodgman <dave.rodgman@arm.com> Sun Jan 14 12:59:49 2024 +0000
committer Dave Rodgman <dave.rodgman@arm.com> Mon Jan 15 11:45:01 2024 +0000
tree 3c3ce129f84c7a782186382f0fbb73a69e7ec877
parent 174eeff235f2d3c8290a5709811669332521685b

Make gcm counter increment more efficient

Signed-off-by: Dave Rodgman <dave.rodgman@arm.com>

library/gcm.c

diff --git a/library/gcm.c b/library/gcm.c
index 20d55c0..c677ca4 100644
--- a/library/gcm.c
+++ b/library/gcm.c
@@ -401,12 +401,9 @@
 /* Increment the counter. */
 static void gcm_incr(unsigned char y[16])
 {
-    size_t i;
-    for (i = 16; i > 12; i--) {
-        if (++y[i - 1] != 0) {
-            break;
-        }
-    }
+    uint32_t x = MBEDTLS_GET_UINT32_BE(y, 12);
+    x++;
+    MBEDTLS_PUT_UINT32_BE(x, y, 12);
 }
 
 /* Calculate and apply the encryption mask. Process use_len bytes of data,