Split any file into a keyless binary block and a 128-bit text key.

---

Any file becomes two objects: a binary block and a short text key. Without the key, the block is useless.

photo.jpg  -->  data.bin + key.txt
  1.05 MB       1.05 MB    102 B

How it works

The file is interpreted as a single large number. The top 128 bits are sliced off to become the key, the rest is saved as a binary block.

File (bytes)  -->  Number  -->  [ data: 128 bits | indices: the rest ]
                                      |                  |
                                   key file          data file

Recovery is a single bitwise operation: (data << count) | indices.

Install

pip install bitsplit

Usage

CLI

# Encode: file -> block + key
bitsplit encode photo.jpg
bitsplit encode photo.jpg -d photo.dat -k photo.key

# Decode: block + key -> file
bitsplit decode restored.jpg
bitsplit decode restored.jpg -d photo.dat -k photo.key

Python API

from bitsplit import encode, decode

# Encode
block, key = encode(open("photo.jpg", "rb").read())
# block = bytes, key = "340079...:8843264:1105424"

# Decode
content = decode(block, key)
open("restored.jpg", "wb").write(content)

Key format

340079864808174098294188674279182237768:8843264:1105424
|                                      |       |
data (128-bit number)                  count   size (bytes)

Why it can't be restored without the key

The key holds 128 bits of data. Brute-forcing 2^128 variants (~3.4 x 10^38) is infeasible — it would take longer than the age of the universe.

Use cases

• Split storage — file on the cloud, key on your device. A breach of one side is useless without the other
• Two-channel transfer — send the block via messenger, the key via SMS. Intercepting one channel reveals nothing
• Offline backups — data on an external drive, key on paper in a safe
• Shared access control — one person holds the key, another holds the block. Both are required to restore the file
• CI/CD secrets — block committed to the repo, key stored in environment variables
• Geo-distribution — block in one data center, key in another

Caution

bitsplit is not encryption. It does not use ciphers, rounds, or key derivation. It splits raw data into two parts — neither part is useful without the other. Think of it as tearing a document in half rather than locking it in a safe. The 128-bit key makes brute-force infeasible, but there is no authentication, no padding, and no protection against tampering. If you need a cryptographic standard (compliance, audits, signatures), use AES or ChaCha20.

Performance

bitsplit uses two bitwise operations with no loops, no block processing, and no rounds — just a single shift and OR. Benchmarked on Apple M2 (8 GB RAM):

Encode

File size	bitsplit	OpenSSL AES-256	OpenSSL ChaCha20	GPG AES-256	age	7-Zip AES-256
1 MB	0.08 s	0.02 s	0.00 s	0.29 s	0.02 s	0.14 s
10 MB	0.04 s	0.05 s	0.03 s	0.45 s	0.01 s	0.53 s
100 MB	0.13 s	0.64 s	0.36 s	2.43 s	0.15 s	4.86 s
1 GB	1.45 s	5.11 s	3.18 s	3.58 s	1.56 s	3.16 s
5 GB	15.6 s	58.8 s	78.6 s	148.5 s	10.5 s	372.2 s

Decode

File size	bitsplit	OpenSSL AES-256	OpenSSL ChaCha20	GPG AES-256	age	7-Zip AES-256
1 MB	0.02 s	0.00 s	0.00 s	0.26 s	0.00 s	0.01 s
10 MB	0.04 s	0.05 s	0.03 s	0.32 s	0.02 s	0.02 s
100 MB	0.08 s	0.49 s	0.34 s	1.09 s	0.16 s	0.09 s
1 GB	1.63 s	4.71 s	4.35 s	1.04 s	3.85 s	0.83 s
5 GB	13.6 s	91.8 s	45.9 s	56.1 s	11.0 s	22.0 s

Peak memory

File size	bitsplit	OpenSSL AES-256	OpenSSL ChaCha20	GPG AES-256	age	7-Zip AES-256
1 MB	14 MB	1.5 MB	1.5 MB	6 MB	7 MB	—
10 MB	18 MB	1.5 MB	1.5 MB	6 MB	7 MB	—
100 MB	20 MB	1.5 MB	1.5 MB	6 MB	7 MB	—
1 GB	24 MB	1.5 MB	1.5 MB	6 MB	7 MB	—
5 GB	21 MB	1.5 MB	1.5 MB	6 MB	7 MB	1.6 GB

Bold = fastest in row. Streaming I/O keeps memory flat at ~20 MB regardless of file size.

All files restored with identical SHA-256 checksums. Pure Python, zero dependencies.

Features

• Zero dependencies — pure Python, standard library only
• Any file — jpg, mp4, zip, exe, anything with bytes
• Output size = input size — no overhead
• Instant — two bitwise operations, no loops
• Key fits in one line — memorize it, write it down, send it in a message
• Custom paths — specify any output/input file names

Requirements

Python 3.11+