BitEncryption

Lightweight C++ byte-array obfuscation using XOR, byte-reversal, and a trailing 3‑byte signature. This is a simple educational utility; it is not a cryptographically secure algorithm.

Project structure

src/
 ├─ bit_encryption.h
 └─ bit_encryption.cpp
legacy/
 └─ bit_encryption_legacy.cpp
example/
 └─ example.cpp
LICENSE
README.md
.gitignore

How it works (at a glance)

Given input bytes and one or more key bytes:

1. Builds an effective key stream of the same length as the input:

• If there are fewer keys than input bytes, keys are repeated (cycled).
• If there are more or equal keys, they are folded by XOR into positions modulo the input length.

2. XORs each input byte with the corresponding effective key byte.
3. Reverses the resulting byte order.
4. Appends a 3‑byte signature 0x3B, 0x2D, 0x29 to mark a valid ciphertext.

Decryption validates the signature, strips it, reverses the bytes, rebuilds the same effective key stream, and XORs to recover the original.

Error handling: on invalid input, methods return an empty vector.

Public API

Class: BitEncryption

• std::vector<uint8_t> encrypt(const std::vector<uint8_t>& originalBytes, const std::vector<uint8_t>& keys);

  • Returns ciphertext with signature appended, or an empty vector on error.

• std::vector<uint8_t> decrypt(const std::vector<uint8_t>& encryptedBytes, const std::vector<uint8_t>& keys);

  • Returns recovered plaintext, or an empty vector on error (e.g., missing/invalid signature).

• std::vector<uint8_t> generateKeys(size_t count);

  • Generates count random bytes in [0, 255] using std::random_device with std::uniform_int_distribution (unbiased). On mainstream Windows/Linux, random_device is typically backed by the OS CSPRNG, but this isn’t guaranteed by the C++ standard.

Signature bytes and size (for reference): 0x3B, 0x2D, 0x29 (size 3).

Build and run

Compile and link src/bit_encryption.cpp with your application and include src/bit_encryption.h. Replace example/example.cpp with your main.

• MSVC (Developer Command Prompt / PowerShell):

cl /std:c++17 /EHsc example/example.cpp src\bit_encryption.cpp /Fe:app.exe

• g++/clang++ (MinGW or Unix-like environments):

g++ -std=c++17 example/example.cpp src/bit_encryption.cpp -o app

Notes and limitations

• This is not secure encryption; it’s a simple XOR-based obfuscation with a fixed signature. Do not use for sensitive data.
• Keys may include 0 values. Allowing 0 ensures a full 8 bits of entropy per byte; XOR by 0 occurs with probability 1/256 and is expected.
• The key folding behavior when providing many keys is intentional; read the implementation if you need a different policy (e.g., truncate or hash keys).

License

This project is released under The Unlicense (public domain). See LICENSE or https://unlicense.org.