commit e6d8db0f41ebed6a3fbb29faca8b42156161f3ad
author Andrzej Kurek <andrzej.kurek@arm.com> Sun Aug 09 23:41:40 2020 -0400
committer Andrzej Kurek <andrzej.kurek@arm.com> Mon Aug 10 02:54:56 2020 -0400
tree 6d633301999596e49d39167b967412f2a448445e
parent 858e4325d2eb55274950e9335d0c08a1326069c2

Change the tinycrypt return values to be below 256

Thanks to this change the produced ASM does not need an additional instruction
to place the constant value in a register, but can compare it directly.
Signed-off-by: Andrzej Kurek <andrzej.kurek@arm.com>

include/tinycrypt/ecc.h

diff --git a/include/tinycrypt/ecc.h b/include/tinycrypt/ecc.h
index 4c20729..f2a5ad6 100644
--- a/include/tinycrypt/ecc.h
+++ b/include/tinycrypt/ecc.h
@@ -85,9 +85,9 @@
 /* Return values for functions, chosen with large Hamming distances between
  * them (especially to SUCESS) to mitigate the impact of fault injection
  * attacks flipping a low number of bits. */
-#define UECC_SUCCESS            0x00FFAAAA
-#define UECC_FAILURE            0x75555555
-#define UECC_FAULT_DETECTED     0x7aaaaaaa
+#define UECC_SUCCESS            0xCD
+#define UECC_FAILURE            0x52
+#define UECC_FAULT_DETECTED     0x3B
 
 /* Word size (4 bytes considering 32-bits architectures) */
 #define uECC_WORD_SIZE 4