Lofer Cipher

A symmetric-key block cipher using Substitution-Permutation Network (SPN) design.

EDUCATIONAL USE ONLY

Build & Run

g++ -std=c++17 -O3 -march=native -I include -o lofer src/main.cpp

Usage

# Basic encrypt/decrypt
./lofer -e input.txt -p "password"
./lofer -d input.txt.enc -p "password"# With options
./lofer -e data.bin --rounds 24 --hash sha512 --iterations 200000 -p "password"
./lofer -D ./docs -r -p "password"# Process directory recursively# Show all options
./lofer --help

Command-line Options

Option	Description
-e <file>	Encrypt file
-d <file>	Decrypt file
-o <output>	Output path
-D <dir>	Process directory
-r	Recursive mode
-p <password>	Password (prompts if omitted)
--rounds <N>	SPN rounds: 8-32 (default: 16)
--hash <type>	sha256 or sha512 (default: sha256)
--iterations <N>	PBKDF2 iterations (default: 100000)
--no-auth	Disable HMAC (not recommended)

API Usage

#include"cipher.hpp"usingnamespacelofer;// Default configurationauto encrypted = encrypt(plaintext, password);
auto decrypted = decrypt(encrypted, password);
// Custom configuration
CipherConfig config;
config.hashAlgo = HashAlgorithm::SHA512;
config.numRounds = 24;
config.pbkdf2Iterations = 200000;
config.useAuthentication = true;
auto encrypted = encrypt(plaintext, password, config);

Algorithm

1. Generate random 16-byte salt
2. Derive keys via PBKDF2-HMAC-SHA256/512
3. For each round: S-box substitution → affine permutation
4. Compute HMAC over ciphertext (Encrypt-then-MAC)
5. Output: salt || ciphertext || HMAC

File Format

+----------+------------+----------+
| Salt | Ciphertext | HMAC |
| 16 bytes | L bytes | 32 bytes |
+----------+------------+----------+