1  ctaes
 2  =====
 3  
 4  Simple C module for constant-time AES encryption and decryption.
 5  
 6  Features:
 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  
12  Performance
13  -----------
14  
15  Compiled 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  
23  Build steps
24  -----------
25  
26  Object code:
27  
28      $ gcc -O3 ctaes.c -c -o ctaes.o
29  
30  Tests:
31  
32      $ gcc -O3 ctaes.c test.c -o test
33  
34  Benchmark:
35  
36      $ gcc -O3 ctaes.c bench.c -o bench
37  
38  Review
39  ------
40  
41  Results of a formal review of the code can be found in http://bitcoin.sipa.be/ctaes/review.zip