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https://github.com/ctz/cifra
A collection of cryptographic primitives targeted at embedded use.
https://github.com/ctz/cifra
Last synced: 12 days ago
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A collection of cryptographic primitives targeted at embedded use.
- Host: GitHub
- URL: https://github.com/ctz/cifra
- Owner: ctz
- License: cc0-1.0
- Created: 2015-01-21T20:27:31.000Z (almost 10 years ago)
- Default Branch: main
- Last Pushed: 2023-10-29T19:36:19.000Z (about 1 year ago)
- Last Synced: 2024-08-04T23:10:45.079Z (3 months ago)
- Language: C
- Homepage:
- Size: 547 KB
- Stars: 333
- Watchers: 30
- Forks: 57
- Open Issues: 11
-
Metadata Files:
- Readme: README.md
- License: COPYING
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README
# Cifra
Cifra is a collection of cryptographic primitives targeted at embedded use.
[](https://travis-ci.org/ctz/cifra)
[](https://cifra.readthedocs.org/en/latest/)
[](https://scan.coverity.com/projects/4324)
[](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