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+Bitsliced AES
+-------------
+
+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.
+
+Some encryption algorithms allow blocks to be operated on in parallel like AES CTR.  So if there is enough input, say 32 blocks,
+then a 32 bit processor can achieve full utilitization by filling all bits in word and enciphering all blocks in parallel.
+
+
+Research
+--------
+
+
+Bitslicing is not a new idea.  It was first done on DES by Eli Biham in 1997 as described by his paper "A Fast New DES Implementation in Software".
+Since then many implementations have been done on AES and other encryption algorithms.  However none are either pubicly available or easily portable.
+
+
+This bitsliced implementation
+-----------------------------
+
+This work exists for education and research.  This repository exists as a reference for people working on bitslicing.
+It is written entirely in C.
+
+Performance measurements done for AES-CTR on a 64 bit 4 GHz Intel 4790 and compiled with GCC 4.8.4.
+
+|                      |footprint | throughput |
+|----------------------|----------|------------|
+|Performance optimized |  12,150 bytes  | 51 cycles/byte |
+|Footprint optimized   | 8,526 bytes | 81 cycles/byte |
+
+Performance could be improved by about 5-10x by writting in assembly and ensuring
+more operations stay in registers rather then spill to memory.
+
+
+Compiling
+----------
+
+Compile the benchmarking program by running:
+
+```bash
+make
+```
+
+Benchmark program requires OpenSSL.
+
+
+Compile the test program by running:
+
+```bash
+make test
+```
+
+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.
+
+