https://github.com/byut/des
An optimized implementation of the Data Encrpytion Standard (DES) in C
https://github.com/byut/des
c cryptography des encryption
Last synced: 7 months ago
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An optimized implementation of the Data Encrpytion Standard (DES) in C
- Host: GitHub
- URL: https://github.com/byut/des
- Owner: byut
- License: mit
- Created: 2023-10-22T18:42:01.000Z (almost 2 years ago)
- Default Branch: main
- Last Pushed: 2024-06-13T16:20:43.000Z (over 1 year ago)
- Last Synced: 2025-01-24T22:34:29.246Z (9 months ago)
- Topics: c, cryptography, des, encryption
- Language: C
- Homepage:
- Size: 18.6 KB
- Stars: 0
- Watchers: 1
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- License: LICENSE
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README
# Data Encryption Standard
An optimized implementation of the Data Encrpytion Standard (DES) in C.
## Overview
To attain optimal efficiency, the algorithm incorporates several optimization
techniques proposed by Eli Biham in his paper titled "A Fast New DES
Implementation in Software."
The core concept is to parallelize encryption operations. The quantity of
encryptions is limited by the hardware employed in the encryption process.
Nonetheless, leveraging widely available 64-bit processors enables the
simultaneous execution of 64 encryptions. To achieve this, we can represent 64
data blocks as a transposed matrix of bits. This approach facilitates encryption
through straightforward bitwise operations, eliminating the need for iterative
processing through each bit 64 times.
Furthermore, we obviate the need for expensive permutations. Instead, we
directly access individual bits as if they were permuted. This eliminates the
need for performing initial permutations or generating subkeys for each round,
resulting in significant time and resource savings during the encryption
process.
Another notable improvement in performance was achieved by employing logic gate
operations within S-boxes as opposed to the traditional approach of using lookup
tables. Moreover, each S-box already includes the P permutation and the E
expansion in its 64-bit result. The implementation of S-boxes within this
algorithm is indeed noteworthy, boasting an impressive average gate count of 56.
The code, credited to Matthew Kwan, was obtained from the following
[website](https://darkside.com.au/bitslice/). You can gain further insights by
consulting his paper on the subject, titled "Reducing the Gate Count of Bitslice
DES." There is an even faster implementation, enhanced by impressive 17%,
that is utilized in the John the Ripper password cracker.
## Building from source
To test this implementation, the project provides a simple demo (see
[main.c](https://github.com/byut/des/blob/main/main.c)):
```bash
mkdir build \
&& gcc -O3 -Iinclude -o build/out main.c src/*.c \
&& build/out \
&& rm -rdf build
```