https://github.com/ellectroid/ecdh-binarycurves-basic

A small library for doing elliptic curve Diffie-Hellman key exchange using binary curves (NOT CONSTANT TIME)
https://github.com/ellectroid/ecdh-binarycurves-basic

Last synced: 6 months ago
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A small library for doing elliptic curve Diffie-Hellman key exchange using binary curves (NOT CONSTANT TIME)

• Host: GitHub
• URL: https://github.com/ellectroid/ecdh-binarycurves-basic
• Owner: ellectroid
• License: unlicense
• Created: 2025-07-09T12:38:32.000Z (7 months ago)
• Default Branch: main
• Last Pushed: 2025-07-09T13:32:05.000Z (7 months ago)
• Last Synced: 2025-07-09T14:43:30.908Z (7 months ago)
• Language: C++
• Size: 18.6 KB
• Stars: 0
• Watchers: 0
• Forks: 0
• Open Issues: 0
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

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README

          
# ECDH-binarycurves-basic

A small library for doing elliptic curve Diffie-Hellman key exchange using binary curves.

## WARNING

This library is not a constant time library. It only gives algebraically correct results!

## Description

A tiny recreational elliptic curve Diffie-Hellman key exchange library.   

Dependencies: none. Doesn't use standard libraries, doesn't use any runtime libraries (even no memset or memcpy), doesn't #include anything at all.  

It should be fully C-compatible C++ code.  

Should work on any platform for which one can compile C or C++.   

Min language requirements: C11/C++11 (only because of alignas)   

There is room for optimization of underlying algorithms for better use of CPU time   

This library can work as a reference   

Tested with curves K-163, B-163, K-233, K-283 (Binary curves only! Prime curves not supported!)   

Tested on desktop   

Tested on ARM Cortex-M7 STM32F746 @ 216MHz:

  - ~1.35KiB peak RAM usage with keys and calculations with 37 bytes allocated per GF(2) vector (e.g. with K-283)

  - ~1.15KiB peak RAM usage with keys and calculations with 32 bytes allocated per GF(2) vector (e.g. with K-233)

  - ~6.5KiB ROM use for debug build

  - ~2.9KiB ROM use for release build

  - Calculating a public key from a private key took around 25 seconds using curve K-233 (curves greater than K-233 seem impractical for it)

 

## Usage

The library doesn't provide curve parameters, but this repository includes library test code that contains parameters for K-163, B-163, K-233 and K-283.   

Make sure to adjust compile-time value GF2_VECTOR_MAX_BYTELEN in galois_field2.h to make sure it fits your GF(2) vector. Use one byte more than required to fit the entire vector.

By default it's 32, so it won't fit K-283 without adjustment.