1 files changed, 16 insertions, 1 deletions

diff --git a/aes.c b/aes.c
index b550ff6..c609c1f 100644
--- a/aes.c
+++ b/aes.c
@@ -131,6 +131,21 @@ static const uint8_t rsbox[256] = {
 
 // The round constant word array, Rcon[i], contains the values given by 
 // x to th e power (i-1) being powers of x (x is denoted as {02}) in the field GF(2^8)
+static const uint8_t Rcon[11] = {
+  0x8d, 0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80, 0x1b, 0x36 };
+
+/*
+ * Jordan Goulder points out in PR #12 (https://github.com/kokke/tiny-AES128-C/pull/12),
+ * that you can remove most of the elements in the Rcon array, because they are unused.
+ *
+ * From Wikipedia's article on the Rijndael key schedule @ https://en.wikipedia.org/wiki/Rijndael_key_schedule#Rcon
+ * 
+ * "Only the first some of these constants are actually used – up to rcon[10] for AES-128 (as 11 round keys are needed), 
+ *  up to rcon[8] for AES-192, up to rcon[7] for AES-256. rcon[0] is not used in AES algorithm."
+ *
+ * ... which is why the full array below has been 'disabled' below.
+ */
+#if 0
 static const uint8_t Rcon[256] = {
   0x8d, 0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80, 0x1b, 0x36, 0x6c, 0xd8, 0xab, 0x4d, 0x9a,
   0x2f, 0x5e, 0xbc, 0x63, 0xc6, 0x97, 0x35, 0x6a, 0xd4, 0xb3, 0x7d, 0xfa, 0xef, 0xc5, 0x91, 0x39,
@@ -148,7 +163,7 @@ static const uint8_t Rcon[256] = {
   0x08, 0x10, 0x20, 0x40, 0x80, 0x1b, 0x36, 0x6c, 0xd8, 0xab, 0x4d, 0x9a, 0x2f, 0x5e, 0xbc, 0x63,
   0xc6, 0x97, 0x35, 0x6a, 0xd4, 0xb3, 0x7d, 0xfa, 0xef, 0xc5, 0x91, 0x39, 0x72, 0xe4, 0xd3, 0xbd,
   0x61, 0xc2, 0x9f, 0x25, 0x4a, 0x94, 0x33, 0x66, 0xcc, 0x83, 0x1d, 0x3a, 0x74, 0xe8, 0xcb, 0x8d };
-
+#endif
 
 /*****************************************************************************/
 /* Private functions:                                                        */