line / aes-gcm-siv Goto Github PK

The C implementation has 5 look-up tables, which combined use 4352 bytes of memory:

// Forward S-box & tables
static uint8_t FSb[256];
static uint32_t FT0[256];
static uint32_t FT1[256];
static uint32_t FT2[256];
static uint32_t FT3[256];

This might not seem like a lot on desktop/laptop/mobile, but is a lot in the context of embedded microcontrollers, which sometimes only have 38 KB of RAM memory in total.

This could be done more efficiently by making the lookup tables static const and having them populated at compile-time. The disadvantage of this is that the hardcoded constants will be harder to audit (but then again, if the constants are wrong, the tests won't pass).