SIMONTOOL

1) Summary

What is simontool?  Simontool is a program that is intended to aid in the development of 
hardware implementations of the Simon cipher; however, it can also encrypt files.  The 
program is now fast due to the overhead of creating simulation data.  The program creates 
Piece-Wise-Linear wave forms that are of an appropriate format for SPICE simulators.  

1.1) Command options

The simontool program is licensed under the GPLv2.
(c) 2015-2017 Brian Degnan, and the Georgia Institute of Technology

   Options for simontool:
    -a       output all PWL files
    -b <arg> configure the block size in bits
    -c <arg> limit clock cycles *
    -d       decryption
    -e       encryption
    -h       help (this page)
    -i <arg> input filename to encrypt/decrypt
    -k <arg> key size in bits
    -l <arg> (experimental) include logfile with name *
    -o <arg> output filename from encrypt/decrypt
    -m <arg> specify block code book type
    -r <arg> (experimental) number of rounds *
    -s <arg> key hex in ASCII
    -t <arg> test hex in ASCII
    -u       hash ASCII (experimental), changes architecture *
    -v <arg> set voltage for PWL data
    -x <arg> (experimental) LaTeX code output where 
             <arg> becomes the prefix for -key.tex and -data.tex files 
    -y       (experimental) printout expanded data and key to stdout  *

    * denotes options that generally should not be used.

1.2) Examples
Test cases use the -t flag that does not expect a file.
    
An example of encryption for Simon 128/128: 
simontool -e -b 128 -k 128 -s 0f0e0d0c0b0a09080706050403020100 -t 
63736564207372656c6c657661727420

An example of decryption for Simon 32/64 that creates strobe files and logs the iterative 
outputs to the file d.txt:
simontool -a -d -b 32 -k 64 -s 4d837db932f2fa04  -t c69be9bb -l d.txt

An example of decryption for Simon 32/64 that outputs the final key and data to stdout:
simontool -d -b 32 -k 64 -s 4d837db932f2fa04  -t c69be9bb -y



2) Functional Description

First and foremost, simontool is a program to assist with the hardware simulation and 
verification of the Simon Cipher.  The program simulates a bit-serial implementation of 
the cipher, as it would be implemented in hardware.  This ads considerable overhead even 
if the strobe files are not being output.  The simontool program simulates every bit and 
key width of the simon cipher.

The simontest.sh script will verify and encryption and decryption functionality of the 
program.  The script is written in BASH and reads from the simontest.data file.

More details regarding the functionality of the program are described in my IEEE papers.

3) File Encryption

The simontool program can be used encrypt and decrypt data files.  The simontool program
assumes that encryption and decryption uses same starting key but from differing points
in the expansion.  For instance, for SIMON32/64, one would encrypt a file, in this case
   simon.c with the command: 
simontool -e -b 32 -k64 -s 1918111009080100 -i simon.c -o simon.c.simon
1918111009080100 is the starting key for encryption, but the resulting key after the
expansion is 4d837db932f2fa04.  Therefore, decryption would use the expanded key:
simontool.elf -d -b 32 -k 64 -s 4d837db932f2fa04 -i simon.c.simon -o simon.c.undo

The code book type selection via the -m option is currently limited CBC, with EBC as the
default.  The -m cbc option add the text " CBC" into the encrypted file header, which is
then auto-detected during decryption.

3.1 File Header Format

When a file is encrypted with simontool, 32-bytes are used for stream information.

The file header as of version 1.0.3 in ASCII:
Header is 32-bytes in total
    8 for the word SIMON
    8 for nothing
    4 for code book type
    4 for offset padding (most likely a value < 8)
    4 for key size information <optional>
    4 for block size information <optional>


4.0  Current Problems

simontool does not make assumptions on how the key and data are initially loaded.  This 
means that the PWL files are created from a loaded state.