This repository contains an implementation of KLEIN lightweight block cipher block cipher written in C language. For information about this cipher please read authors' paper: KLEIN: A New Family of Lightweight Block Ciphers.

KLEIN implementation can be compiled into both static and dynamic library. To build (S)KLEIN libraries call:

make library

Header file (sklein.h) and two versions of library (libsklein.a and libsklein.so) will be placed in output directory (./build).

Simple demo application that shows how to use this implementation can be found in ./demo/demo.c. To build demo application call:

make demo

Executable file will be stored in ./build/sklein-demo. Currently demo presents only usage of KLEIN-64.

To validate implemented encryption and decryption test vectors from KLEIN specification (Appendix A.) are used. All test related files are stored in ./test directory. Test vectors are declared and defined in test-vectors.h and test-vectors.c respectively. Simple "test engine" implementation can be found in main.c.

To build and launch tests one has to call:

make tests

Test binary will be created in ./build/sklein-tests directory and executed.

All necessary SKLEIN data types and functions are defined in *sklein.h" header file. SKLEIN API is mainly composed of following 5 functions:

sklein_t sklein_create(int km);

int sklein_set_key(sklein_t crypter, const uint8_t *mkey, uint8\_t k\_length);

int sklein\_encrypt\_block(sklein\_t crypter, uint8\_t *block);

int sklein_decrypt_block(sklein_t crypter, uint8_t *block);

void sklein\_destroy(sklein\_t crypter);

Please see mentioned header for more details.

This library provides only implementation of KLEIN block cipher with support of one block only encryption/decryption based on algorith specification. To encrypt 8B (one block) of data using KLEIN-64 following steps are needed:

    sklein_t crypter = sklein_create(KLEIN_MODE_64);
    if (crypter == NULL)
    {
        printf("ERROR: Failed to create KLEIN-64\n");
        return 1;
    }

    uint8_t data64[] = {0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff};
    uint8_t key64[] = {0x12, 0x34, 0x56, 0x78, 0x90, 0xab, 0xcd, 0xef};

    int result = 0;
    result = sklein_set_key(crypter, key64, sizeof(key64));
    if (result != KLEIN_RESULT_OK)
    {
        printf("ERROR: Failed to set key: %d\n", result);
        return 1;
    }

    result = sklein_encrypt_block(crypter, data64);
    if (result != KLEIN_RESULT_OK)
    {
        printf("ERROR: Failed to crypt\n");
        return 1;
    }

In similar way encrypted data can be decrypted with use of provided implementation:

    sklein_t crypter = sklein_create(KLEIN_MODE_64);
    if (crypter == NULL)
    {
        printf("ERROR: Failed to create KLEIN-64\n");
        return 1;
    }

    uint8_t data64[] = {0x59, 0x23, 0x56, 0xC4, 0x99, 0x71, 0x76, 0xC8};
    uint8_t key64[] = {0x12, 0x34, 0x56, 0x78, 0x90, 0xab, 0xcd, 0xef};

    int result = 0;
    result = sklein_set_key(crypter, key64, sizeof(key64));
    if (result != KLEIN_RESULT_OK)
    {
        printf("ERROR: Failed to set key: %d\n", result);
        return 1;
    }

    result = sklein_decrypt_block(crypter, data64);
    if (result != KLEIN_RESULT_OK)
    {
        printf("ERROR: Failed to decrypt\n");
        return 1;
    }

Please see provided demo/demo.c file for full encryption/decryption example.

For encrypting data sets larger than one block (8B) KLEIN cipher has been enclosed in Cipher Block Chaining algorithm. It uses 8B Initialization Vector and encrypts blocks of N*8B length.

Functions below have been added specificaly for CBC mode:

int sklein_set_iv(sklein_t crypter, const uint8_t *iv);

int sklein_cbc_encrypt_data(sklein_t crypter, uint8_t *data, size_t len);

int sklein_cbc_decrypt_data(sklein_t crypter, uint8_t *data, size_t len);

Both encrypt and decrypt functions are placing encryption result in input data buffer.

This implementation has been written "just for fun" and is published "AS IS". It is not optimized neither analyzed for security weakness.

Code form this repository can be included in other projects in parts or as a whole but it is not recommended to use it in production environment.

If you need to contact me feel free to write me an email: markamdev.84#dontwantSPAM#gmail.com