README.md
1ctaes
2=====
3
4Simple C module for constant-time AES encryption and decryption.
5
6Features:
7* Simple, pure C code without any dependencies.
8* No tables or data-dependent branches whatsoever, but using bit sliced approach from https://eprint.iacr.org/2009/129.pdf.
9* Very small object code: slightly over 4k of executable code when compiled with -Os.
10* Slower than implementations based on precomputed tables or specialized instructions, but can do ~15 MB/s on modern CPUs.
11
12Performance
13-----------
14
15Compiled with GCC 5.3.1 with -O3, on an Intel(R) Core(TM) i7-4800MQ CPU, numbers in CPU cycles:
16
17| Algorithm | Key schedule | Encryption per byte | Decryption per byte |
18| --------- | ------------:| -------------------:| -------------------:|
19| AES-128 | 2.8k | 154 | 161 |
20| AES-192 | 3.1k | 169 | 181 |
21| AES-256 | 4.0k | 191 | 203 |
22
23Build steps
24-----------
25
26Object code:
27
28 $ gcc -O3 ctaes.c -c -o ctaes.o
29
30Tests:
31
32 $ gcc -O3 ctaes.c test.c -o test
33
34Benchmark:
35
36 $ gcc -O3 ctaes.c bench.c -o bench
37
38Review
39------
40
41Results of a formal review of the code can be found in http://bitcoin.sipa.be/ctaes/review.zip
42