LivingEntropyCipher (LEC)

A Structure‑Independent Cipher with Evolving Entropy
Reference Implementation (C Language)

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Overview

LivingEntropyCipher (LEC) is a symmetric encryption scheme that does not rely on mathematical hardness assumptions or random number generators.
Instead, LEC uses a 100 KB evolving table that mutates irreversibly during encryption and decryption.

This reference implementation provides:

• Minimal and clean C implementation of the LEC core
• Fully deterministic behavior matching the original C# prototype
• Structure‑independent design with no algebraic attack surface
• Built‑in table fingerprinting for synchronization and tamper detection

LEC is a volume‑based cryptographic primitive where security emerges from the enormous state space of the evolving table.

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Key Features

• 100 KB evolving table (256^100000 state space)
• History‑dependent irreversible mutation
• No RNG required
• No algebraic structure
• Strong statistical properties:
  • Entropy: 7.99 / 8.0
  • Correlation: 0.0003
• TableHash (FNV‑1a) for synchronization
• Identical behavior to the original C# implementation

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Files

Documentation

• doc/LivingEntropyCipher(English).pdf
• doc/LivingEntropyCipher(Japanese).pdf

Source Code

• src/lec.h
• src/lec.c

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Directory Structure

LEC/
├─ doc/
│   ├─ LivingEntropyCipher(English).pdf
│   └─ LivingEntropyCipher(Japanese).pdf
│
└─ src/
    ├─ lec.h
    └─ lec.c

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Algorithm Summary

For each byte:

• Compute key from evolving table
• XOR input with key
• Mutate table using ciphertext
• Advance pointer and index

The table evolves every byte, ensuring:

• No state repeats
• No reversible structure exists
• No algebraic shortcut is possible

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C API

Initialization

int lec_init(LECContext* ctx, uint64_t seed, int jump, uint8_t mask);

Encryption / Decryption

int lec_encrypt_buffer(LECContext* ctx, const uint8_t* in, uint8_t* out, size_t len);
int lec_decrypt_buffer(LECContext* ctx, const uint8_t* in, uint8_t* out, size_t len);

Table Fingerprint

uint32_t lec_get_fingerprint(const LECContext* ctx);

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Example Usage (C)

#include "lec.h"
#include <stdio.h>

int main() {
    LECContext ctx;
    lec_init(&ctx, 123456789ULL, 7, 0x55);

    uint8_t input[] = "Hello LEC!";
    uint8_t encrypted[64];
    uint8_t decrypted[64];

    lec_encrypt_buffer(&ctx, input, encrypted, 10);

    lec_init(&ctx, 123456789ULL, 7, 0x55);
    lec_decrypt_buffer(&ctx, encrypted, decrypted, 10);

    printf("Decrypted: %s\n", decrypted);
    return 0;
}

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Security Notes

• Not based on algebraic hardness
• No known quantum algorithm can exploit its structure
• Security derives from:
  • irreversible table evolution
  • massive state space
  • history‑dependent mutation

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License

MIT License (recommended)

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Reference

This implementation corresponds to the paper:
“LivingEntropyCipher (LEC): A Structure‑Independent Cipher with Evolving Entropy”
NS (2026)