Bitslicing is a technique to compute steps in an algorithm 1 bit at a time. Each bit in a processor word would be a part of a different data stream for that particular algorithm. It is attractive because then it can run many different streams in parallel (depending on the word length). E.g. a 32 bit word length can compute 32 different streams in parallel.

Because every stream is transposed, it becomes easy to enumerate them and decide which ones can act as redundant or constant slices for detection of fault injections.

You can see different implementations of the fault resistance added to the bitsliced implementation by looking at the different branches:

• unprotected
• redundant slices
• pipelined
• shuffled pipelined

See our paper:

C. Patrick, B. Yuce, N. Farhady Ghalaty, P. Schaumont, "Lightweight Fault Attack Resistance in Software Using Intra-Instruction Redundancy," Selected Areas in Cryptography (SAC 2016), St. John's, Canada, August 2016.

Performance measurements done for a fault resistant AES-CTR on a 64 bit 4 GHz Intel 4790 and compiled with GCC 4.8.4. Overhead was calculated in reference to the (unprotected) bitsliced implementation.

The amount of redundant slices and number of rounds to check are decided during run time. The idea is to at first have a small fault detection at first to optimize performance but then increase redundancy dynamically in the advent of a fault injection.

Performance could be improved by about 5-10x by writting in assembly and ensuring more operations stay in registers rather then spill to memory.

Compile the benchmarking program by running:

make

Benchmark program requires OpenSSL.

Compile the test program by running:

make test

Compile it for measuring the AES implementation overhead:

make footprint

Change to the word length of your processor by editing the WORD_SIZE macro in bs.h. Optimize for footprint by using -O2 instead of -O3 in the Makefile and also deleting the -DUNROLL_TRANSPOSE flag.

Copyright (c) 2016, Conor Patrick, Bilgiday Yuce, Nahid Farhady Ghalaty, Patrick Schaumont All rights reserved.

C. Patrick, B. Yuce, N. Farhady Ghalaty, P. Schaumont, "Lightweight Fault Attack Resistance in Software Using Intra-Instruction Redundancy," Selected Areas in Cryptography (SAC 2016), St. John's, Canada, August 2016.

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