tree 255ab27a26d5eb32b7accbc38690c9a468b95002
parent ddc6e52cc1f3720a08d2d58d4f6ad61a18c24eb7
author Jussi Kivilinna <jussi.kivilinna@haltian.com> 1447339111 +0200
committer Hanno Becker <hanno.becker@arm.com> 1496845771 +0100

Add option to use smaller AES tables (table sizes reduced by 6144 bytes)

This patch adds MBEDTLS_AES_SMALL_TABLES option to reduce number of AES
look-up tables and thus save 6 KiB of memory. Enabling this option
cause performance hit MBEDTLS_AES_SMALL_TABLES of ~7% on ARM and ~15%
on x86-64.

Benchmark on Cortex-A7 (armhf):

Before:
  AES-CBC-128              :      14394 Kb/s,          0 cycles/byte
  AES-CBC-192              :      12442 Kb/s,          0 cycles/byte
  AES-CBC-256              :      10958 Kb/s,          0 cycles/byte

After:
  AES-CBC-128              :      13342 Kb/s,          0 cycles/byte
  AES-CBC-192              :      11469 Kb/s,          0 cycles/byte
  AES-CBC-256              :      10058 Kb/s,          0 cycles/byte

Benchmark on Intel Core i5-4570 (x86_64, 3.2 Ghz, no turbo):

Before:
  AES-CBC-128              :     215759 Kb/s,         14 cycles/byte
  AES-CBC-192              :     190884 Kb/s,         16 cycles/byte
  AES-CBC-256              :     171536 Kb/s,         18 cycles/byte

After:
  AES-CBC-128              :     185108 Kb/s,         16 cycles/byte
  AES-CBC-192              :     162839 Kb/s,         19 cycles/byte
  AES-CBC-256              :     144700 Kb/s,         21 cycles/byte