# cifra **Repository Path**: gujin__2020/cifra ## Basic Information - **Project Name**: cifra - **Description**: No description available - **Primary Language**: Unknown - **License**: CC0-1.0 - **Default Branch**: main - **Homepage**: None - **GVP Project**: No ## Statistics - **Stars**: 0 - **Forks**: 0 - **Created**: 2025-08-20 - **Last Updated**: 2025-08-20 ## Categories & Tags **Categories**: Uncategorized **Tags**: None ## README # Cifra Cifra is a collection of cryptographic primitives targeted at embedded use. [![Build Status](https://travis-ci.org/ctz/cifra.svg?branch=main)](https://travis-ci.org/ctz/cifra) [![Documentation](https://readthedocs.org/projects/pip/badge/)](https://cifra.readthedocs.org/en/latest/) [![Analysis Status](https://scan.coverity.com/projects/4324/badge.svg)](https://scan.coverity.com/projects/4324) [![Coverage Status](https://coveralls.io/repos/ctz/cifra/badge.svg?branch=coveralls-scan)](https://coveralls.io/r/ctz/cifra?branch=coveralls-scan) ## Aims In order of descending emphasis, cifra aims for: * **Clarity** and **simplicity**. * Countermeasures for side channel leaks inherent in some algorithms. * Suitability for embedded use. Particularly: cifra uses an absolute minimum of the standard C library and is reasonably efficient with respect to code and data space. ## Features * **AES** in the **GCM**, **CCM**, **EAX** and **OCB3** authenticated encryption modes. * **NORX** authenticated encryption system. * **SHA224**, **SHA256**, **SHA384** and **SHA512** hash functions (including **HMAC** and **PBKDF2**). * **SHA3-224**, **SHA3-256**, **SHA3-384**, **SHA3-512** hash functions (FIPS 202 compatible). * **ChaCha20** and **Salsa20** stream ciphers. * **Poly1305** one time MAC. * 100% code coverage by line, zero static analysis defects, valgrind-clean. Additionally cifra imports curve25519 from elsewhere (μNaCl, NaCl, tweetNaCl, Adam Langley's curve25519-donna) for comparison between various implementations on embedded targets. ## Documentation Available at [Read the Docs](https://cifra.readthedocs.org/en/latest/). ## Testing There is quite a lot of testing available: * **Host builds**: run `make test` in the `src` directory. This builds and runs assorted test programs. * **Emulated embedded builds**: run `make test` in the `src/arm` directory. This expects to find `qemu-system-gnuarmeclipse` on the path. These tests assume a Cortex-M3 target. * **Cortex-M0 on-target tests**: run `make test.stm32f0` in the `src/arm` directory. This expects to find `openocd` on the path, with an STM32F0xx attached via stlinkv2. It uses ARM semihosting to report results. * **Cortex-M3/4 on-target tests**: run `make test.stm32f1` or `make test.stm32f3` as above. Additionally all embedded targets expect to find the `arm-none-eabi` toolchain to be on the path. ## Measurements All measurements performed at `-Os` (optimise for space), on the following MCUs: Core | Part number | Price (1s) | Max clock | Flash | SRAM ---------- | ------------- | ------------ | ---------- | ----- | ----- Cortex-M0 | STM32F030F4P6 | 1.17EUR | 48MHz | 16KB | 4KB Cortex-M3 | STM32F103C8T6 | 2.87EUR | 72MHz | 64KB | 20KB Cortex-M4F | STM32F303K6T6 | 4.53EUR | 72MHz | 32KB | 12KB More measurements are available for AEAD modes on my blog post: [Benchmarking Modern Authenticated Encryption on €1 devices](http://jbp.io/2015/06/01/modern-authenticated-encryption-for-1-euro/). ## AES This test does a key schedule, then encrypts one block. ### 128-bit key Core | Cycles (key schedule + block) | Cycles (key schedule) | Cycles (block) | Stack | Code size ---------- | ----------------------------- | --------------------- | -------------- | ----- | --------- Cortex-M0 | 7156 | 2147 | 5009 | 312B | 1020B Cortex-M3 | 4692 | 1591 | 3101 | 300B | 960B Cortex-M4F | 4591 | 1571 | 3020 | 300B | 960B ### 256-bit key Core | Cycles (key schedule + block) | Cycles (key schedule) | Cycles (block) | Stack | Code size ---------- | ----------------------------- | --------------------- | -------------- | ----- | --------- Cortex-M0 | 10611 | 3650 | 6961 | 396B | 1100B Cortex-M3 | 6735 | 2450 | 4285 | 380B | 1048B Cortex-M4F | 6588 | 2416 | 4172 | 380B | 1048B ## AES128-GCM This test encrypts and authenticates a 16 byte message, with 16 bytes additionally authenticated data. It includes the initial key schedule. Core | Cycles | Stack | Code size ---------- | ------ | ----- | --------- Cortex-M0 | 57022 | 796B | 2600B Cortex-M3 | 44306 | 812B | 2644B Cortex-M4F | 43657 | 812B | 2644B ## AES128-EAX This test encrypts and authenticates a 16 byte message, with 16 bytes additionally authenticated data. It includes the initial key schedule. Core | Cycles | Stack | Code size ---------- | ------ | ----- | --------- Cortex-M0 | 50564 | 932B | 2836B Cortex-M3 | 32855 | 932B | 2780B Cortex-M4F | 32159 | 932B | 2780B ## AES128-CCM This test encrypts and authenticates a 16 byte message, with 16 bytes additionally authenticated data. It includes the initial key schedule. Core | Cycles | Stack | Code size ---------- | ------ | ----- | --------- Cortex-M0 | 37677 | 772B | 2280B Cortex-M3 | 24462 | 780B | 2256B Cortex-M4F | 23949 | 780B | 2256B ## NORX32 This test encrypts and authenticates a 16 byte message, with 16 bytes additionally authenticated data. Core | Cycles | Stack | Code size ---------- | ------ | ----- | --------- Cortex-M0 | 10692 | 320B | 1636B Cortex-M3 | 6909 | 320B | 1820B Cortex-M4F | 6855 | 320B | 1820B ## ChaCha20 This test encrypts a 64 byte message. Core | Cycles | Stack | Code size ---------- | ------ | ----- | --------- Cortex-M0 | 5981 | 564B | 1416B Cortex-M3 | 3487 | 544B | 1328B Cortex-M4F | 3468 | 544B | 1328B (For comparison with AES, add an AES256 key schedule plus 4 blocks. That's about 33K cycles.) ## Salsa20 This test encrypts a 64 byte message. Core | Cycles | Stack | Code size ---------- | ------ | ----- | --------- Cortex-M0 | 6173 | 560B | 1412B Cortex-M3 | 3320 | 552B | 1272B Cortex-M4F | 3311 | 552B | 1272B ## SHA256 This test hashes the empty string (one compression function invocation). Core | Cycles | Stack | Code size ---------- | ------ | ----- | --------- Cortex-M0 | 11561 | 312B | 1760B Cortex-M3 | 6530 | 300B | 1708B Cortex-M4F | 6278 | 300B | 1708B ## SHA512 This test hashes the empty string (one compression function invocation). Core | Cycles | Stack | Code size ---------- | ------ | ----- | --------- Cortex-M0 | 38447 | 796B | 2888B Cortex-M3 | 28771 | 836B | 2988B Cortex-M4F | 28777 | 836B | 2980B ## SHA3-256 This test hashes the empty string (one sponge permutation). Core | Cycles | Stack | Code size ---------- | ------ | ----- | --------- Cortex-M0 | 93648 | 848B | 2212B Cortex-M3 | 74321 | 856B | 2164B Cortex-M4F | 72215 | 856B | 2140B ## SHA3-512 This test hashes the empty string (one sponge permutation). Core | Cycles | Stack | Code size ---------- | ------ | ----- | --------- Cortex-M0 | 92565 | 880B | 2212B Cortex-M3 | 73509 | 888B | 2164B Cortex-M4F | 71419 | 888B | 2140B ## HMAC-SHA256 This test computes a MAC with a 32 byte key over the message "hello world". Core | Cycles | Stack | Code size ---------- | ------ | ----- | --------- Cortex-M0 | 48924 | 1328B | 2200B Cortex-M3 | 28333 | 1324B | 2132B Cortex-M4F | 27337 | 1324B | 2132B ## Poly1305-AES This test computes a MAC with a 32 byte key over the message "hello world". It includes the AES nonce processing. Core | Cycles | Stack | Code size ---------- | ------ | ----- | --------- Cortex-M0 | 15719 | 704B | 1920B Cortex-M3 | 11328 | 696B | 1964B Cortex-M4F | 10706 | 696B | 1932B ## Curve25519 This test is one point multiplication. This uses the implementation from [μNaCl](http://munacl.cryptojedi.org/curve25519-cortexm0.shtml) by Düll, Haase, Hinterwälder, Hutter, Paar, Sánchez and Schwabe. Core | Cycles | Stack | Code size ---------- | ------- | ----- | --------- Cortex-M0 | 4070271 | 464B | 5596B Cortex-M3 | 3720363 | 448B | 5536B Cortex-M4F | 3720105 | 448B | 5536B See [curve25519-shootout](curve25519-shootout.md) for comparitive measurements for other curve25519 implementations. ## C library requirements Cifra requires `memcpy`, `memset`, and `abort`. ## Future * ~~Keccak hash function (aka SHA3)~~. * ~~Poly1305 one-time MAC~~. * Constant time curve25519 for Cortex-M4F using the FPU. * Constant time curve25519 for Cortex-M3 (avoiding the variable-time multiplier). ## Notable past bugs/advisories * [Issue #2](https://github.com/ctz/cifra/issues/2): in all versions before commit [d62aa26e](https://github.com/ctz/cifra/commit/d62aa26e2c3c49e5b8a4298644cff290406d9357) (September 16th 2015) too much padding was added when hashing messages of certain lengths. Specifically, messages whose length satisfied `len % 64 = 55` for SHA1/SHA224/SHA256 or `len % 128 = 119` for SHA384/SHA512. SHA3 was not affected. Better testing is now in place. * [Issue #3](https://github.com/ctz/cifra/issues/3): in all versions before commit [82d77cd8](https://github.com/ctz/cifra/commit/82d77cd8323f6d4473fcb68517752a778970138d) (April 16th 2016) EAX would produce wrong tags for empty AADs or messages. The underlying CMAC is now more resistant to this case. * [Issue #6](https://github.com/ctz/cifra/issues/6): in all versions before commit [b6cdf9f3](https://github.com/ctz/cifra/commit/b6cdf9f3dcf693fbc243c5f341ea27114caf869a) the chacha20poly1305 construction would produce incorrect tags for some message or AAD lengths. These case weren't covered by the standard test vectors, so extra tests have been added computed with libsodium. * [Issue #11](https://github.com/ctz/cifra/issues/11): in all versions before commit [df1e4130](https://github.com/ctz/cifra/commit/df1e4130722943b15563e92a0595b31c603aa34d) our salsa20 used incorrect internal ordering when constructing the nonce. The correct ordering is apparently not specified by the specification or covered by test vectors. Additional tests have been generated from libsodium. ## License [CC0](https://creativecommons.org/publicdomain/zero/1.0/). Please attribute the author. This is a request only, and not a license term. ## Author Joseph Birr-Pixton