A single-header C99 library for generating Blowfish tables, so you don't need to hardcode them into your projects. Allows arbitrary table sizes to handle modified forms of the algorithm, with no guarantees on accuracy for larger sizes than the usual 18 subkey + 4x256 S-Box configuration.
Relatively slow; see the Performance section below.
For best results, use OpenMP, as mentioned in the Installation section below.
Include blowfish-tables.h in a source file and pass the compiler option -fopenmp on build, or /openmp with MSVC. The library can be included without OpenMP compiler options, but it will only use a single core.
unsigned int pArray[18];
MakeBlowfishPArray(pArray, ARRAY_SIZE(pArray));
unsigned int sBoxes[4][256];
MakeBlowfishSBoxes(&sBoxes[0][0], ARRAY_SIZE(sBoxes), ARRAY_SIZE(sBoxes[0]), ARRAY_SIZE(pArray));- You don't want a file with lookup tables in your repo?
- You're reading this in 2040 and it takes less than a second for this to run on most machines?
- You want more or larger substitution boxes or P-arrays -- even though I can't guarantee this generates them accurately?
- You want to free the tables after using them to save on memory -- hardcoding them would mean a permanent 0-3kB addition to your binary over this.
- You want to make it harder to determine that your program uses Blowfish by not including hardcoded S-boxes in your binary (the S-boxes will still be in memory unless you free them when you're done using them).
- It was interesting to write, and I learned some things about C, assembly, optimization, and OpenMP.
On the typical configuration -- an 18-subkey P-array and 4 256-subkey substitution boxes -- it takes between 3 and 5 seconds to generate both tables on a 4-core Intel Core i5-7500.
With OpenMP disabled, this runs in around 16 seconds on the same CPU.