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The SIMON and SPECK Families of Block Ciphers

SIMON and SPECK are families of lightweight block ciphers, each of which comes in a variety of widths and key sizes. The aim of SIMON and SPECK is to fill the need for secure, flexible, and analyzable lightweight block ciphers that perform well on a wide range of current and future platforms.

This repository hosts general information about the algorithms with pointers to more detailed information available in other repositories or papers. The newest publication update can be found here: SIMON and SPECK 6 Mar 2019

Presentations and Papers


The implementation guide provides reference code for SIMON and SPECK(64- and 128-bit block sized variants), including code for key scheduling, encryption, and decryption. It also describes the intended word ordering, and provides detailed test vectors and useful tips for improving performance on some ARM and x86 processors.

Higher-end Software

The simon-speck-supercop repository includes X86 and ARM implementations using the SSE4.2, AVX2, and NEON instruction sets for high performance. While the implementations are structured for the SUPERCOP benchmarking toolkit, they should be adaptable to other systems.


The University of Luxembourg Fair Evaluation of Lightweight Cryptographic Systems (FELICS) project includes our contributions of a range of small and fast implementations of SIMON and SPECK for the 8-bit AVR, 16-bit MSP430, and 32-bit Cortex-M microcontrollers.


We have unreleased implementations of SIMON and SPECK for ASICs and FPGAs that have been documented in our papers. The team is glad to answer questions about ASIC and FPGA implementation of the algorithms.

Contact Us

SIMON and SPECK are products of the National Security Agency's Research Directorate, produced as part of our Information Assurance research mission. Contact one of the following members of the SIMON and SPECK team with any questions:

Name Email
Ray Beaulieu
Doug Shors
Jason Smith
Stefan Treatman-Clark
Bryan Weeks
Louis Wingers

Intellectual Property

SIMON and SPECK are free from any intellectual property restrictions.

This Work was prepared by a United States Government employee and, therefore, is excluded from copyright by Section 105 of the Copyright Act of 1976.

Copyright and Related Rights in the Work worldwide are waived through the CC0 1.0 Universal license.




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