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	ctaes
	=====

	Simple C module for constant-time AES encryption and decryption.

	Features:
	* Simple, pure C code without any dependencies.
	* No tables or data-dependent branches whatsoever, but using bit sliced approach from https://eprint.iacr.org/2009/129.pdf.
	* Very small object code: slightly over 4k of executable code when compiled with -Os.
	* Slower than implementations based on precomputed tables or specialized instructions, but can do ~15 MB/s on modern CPUs.

	Performance
	-----------

	Compiled with GCC 5.3.1 with -O3, on an Intel(R) Core(TM) i7-4800MQ CPU, numbers in CPU cycles:

	\| Algorithm \| Key schedule \| Encryption per byte \| Decryption per byte \|
	\| --------- \| ------------:\| -------------------:\| -------------------:\|
	\| AES-128 \| 2.8k \| 154 \| 161 \|
	\| AES-192 \| 3.1k \| 169 \| 181 \|
	\| AES-256 \| 4.0k \| 191 \| 203 \|

	Build steps
	-----------

	Object code:

	$ gcc -O3 ctaes.c -c -o ctaes.o

	Tests:

	$ gcc -O3 ctaes.c test.c -o test

	Benchmark:

	$ gcc -O3 ctaes.c bench.c -o bench

	Review
	------

	Results of a formal review of the code can be found in http://bitcoin.sipa.be/ctaes/review.zip