commit 9b20c6fcc120c1d30963680b32ed263d219e86be
author Tom Cosgrove <tom.cosgrove@arm.com> Tue Jul 04 08:34:12 2023 +0100
committer GitHub <noreply@github.com> Tue Jul 04 08:34:12 2023 +0100
tree fb82023152c1f9fde5d463eb9b506ee0d24246ae
parent 9cf17dad9d32dc4cedbac0d25ea57d2006a3a34b
parent fe944ce2d883c8c178ee978ec3dd75c5b65a6a6d

Merge pull request #7840 from yanrayw/7381_aes_gen_table

AES: use uint8_t for array of pow and log to save RAM usage

library/aes.c

diff --git a/library/aes.c b/library/aes.c
index 6f9033c..a7bc8d5 100644
--- a/library/aes.c
+++ b/library/aes.c
@@ -391,25 +391,26 @@
 
 static void aes_gen_tables(void)
 {
-    int i, x, y, z;
-    int pow[256];
-    int log[256];
+    int i;
+    uint8_t x, y, z;
+    uint8_t pow[256];
+    uint8_t log[256];
 
     /*
      * compute pow and log tables over GF(2^8)
      */
     for (i = 0, x = 1; i < 256; i++) {
         pow[i] = x;
-        log[x] = i;
-        x = MBEDTLS_BYTE_0(x ^ XTIME(x));
+        log[x] = (uint8_t) i;
+        x ^= XTIME(x);
     }
 
     /*
      * calculate the round constants
      */
     for (i = 0, x = 1; i < 10; i++) {
-        RCON[i] = (uint32_t) x;
-        x = MBEDTLS_BYTE_0(XTIME(x));
+        RCON[i] = x;
+        x = XTIME(x);
     }
 
     /*
@@ -421,13 +422,13 @@
     for (i = 1; i < 256; i++) {
         x = pow[255 - log[i]];
 
-        y  = x; y = MBEDTLS_BYTE_0((y << 1) | (y >> 7));
-        x ^= y; y = MBEDTLS_BYTE_0((y << 1) | (y >> 7));
-        x ^= y; y = MBEDTLS_BYTE_0((y << 1) | (y >> 7));
-        x ^= y; y = MBEDTLS_BYTE_0((y << 1) | (y >> 7));
+        y  = x; y = (y << 1) | (y >> 7);
+        x ^= y; y = (y << 1) | (y >> 7);
+        x ^= y; y = (y << 1) | (y >> 7);
+        x ^= y; y = (y << 1) | (y >> 7);
         x ^= y ^ 0x63;
 
-        FSb[i] = (unsigned char) x;
+        FSb[i] = x;
         RSb[x] = (unsigned char) i;
     }
 
@@ -436,8 +437,8 @@
      */
     for (i = 0; i < 256; i++) {
         x = FSb[i];
-        y = MBEDTLS_BYTE_0(XTIME(x));
-        z = MBEDTLS_BYTE_0(y ^ x);
+        y = XTIME(x);
+        z = y ^ x;
 
         FT0[i] = ((uint32_t) y) ^
                  ((uint32_t) x <<  8) ^