averykhoo / plaintext-file-fragmentation

turns any file (or directory of files) into a bunch of small plaintext files

plaintext file fragmentation

what and why

• converts a file or folder into a bunch of ascii plaintext files, and vice versa
• lets you bypass restrictions on file types
• note that you may get in trouble for bypassing restrictions and that's entirely on you

requirements

• python 3.6

usage

on the first PC

• (if input folder does not exist) run encode.bat to create input folder
• copy files or directories into input folder
• run encode.bat (about 1 min per 100 MB)
• your files will be archived to input_archive
• transfer text files in ascii85_encoded to the other pc

on the second PC

• (if ascii85_encoded folder does not exist) run decode.bat to create ascii85_encoded folder
• move text files to ascii85_encoded
• run decode.bat (about 1.5 min per 100 MB)
• take files out from output_decoded

how it works

frag_encode.py

1. tar and gzip input folder to .tgz file on disk
2. break file into random-sized chunks
3. encrypt each chunk separately using the rc4-drop stream cipher (randomized salt and IV per-file)
4. a85 encode each encrypted chunk
5. write each encoded chunk to a text file (with metadata as json in header line)
6. backup original input files to a timestamped folder

frag_decode.py

1. the above steps in reverse
2. allows you to decode multiple sets of chunks in one go
3. decoded files are in a folder named according to the datetime you encoded it

manual alternative

1. zip your file (right-click > send to > compressed folder)
2. certutil -encode -v archive.zip b64.txt
3. transfer b64.txt to your other PC
4. certutil -decode -v b64.txt archive.zip

todo:

• better encryption than rc4, but not too slow
  • so i'm currently using rc4 because it's easy to implement in pure python, reasonably fast, and there aren't any stream ciphers in the builtins
  • maybe chacha
    • check if it succeeds on the test vectors
  • mitigating factors:
    • we're using rc4-drop
    • the key is effectively random
    • the key is the full 256 bytes long
    • the stream is limited to less than 2**25 bytes
• setup logging, or provide receipts when zipping/unzipping?
• unified text fragment class for reading and writing?