135 lines
4.9 KiB
Markdown
135 lines
4.9 KiB
Markdown
# sha-2 [](https://travis-ci.com/amosnier/sha-2)
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## Disclaimer
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The SHA256 implementation used in thsi project is taken from https://github.com/amosnier/sha-2. Check the appropriate license file.
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## Contents
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SHA-2 algorithm implementations.
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At the moment, only SHA-256 is implemented.
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## NEW: streaming API
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In response to [an enhancement
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request](https://github.com/amosnier/sha-2/issues/9), a new streaming
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API has been created.
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The following code is a silly but complete example:
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```C
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struct Sha_256 sha_256;
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uint8_t hash[32];
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sha_256_init(&sha_256, hash);
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sha_256_write(&sha_256, "ab", strlen("ab"));
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sha_256_write(&sha_256, "c", strlen("c"));
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sha_256_close(&sha_256);
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```
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That is the equivalent of the (of course still supported) legacy way:
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```C
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uint8_t hash[32];
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calc_sha_256(hash, "abc", strlen("abc"));
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```
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See [header file](https://github.com/amosnier/sha-2/blob/master/sha-256.h)
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for more information.
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Since the streaming API is a generalization of the non-streaming one,
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the latter has been ported to the former, without measurable performance
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impact. However, [a legacy
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branch](https://github.com/amosnier/sha-2/tree/legacy) has been created
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in order to make the legacy implementation easily available. If you can
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measure a significant difference between the two, please post an issue.
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## Design criteria
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- Easy to test, include in any project, compile and link.
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- ANSI C with as little specific C99 as possible (e.g. extended
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integer types are used, but not bool).
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- Portable. Makes no assumptions on the target system's endianess or
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word size.
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- The SHA-256 implementation is a straightforward implementation of
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the algorithm specified on
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[Wikipedia](https://en.wikipedia.org/wiki/SHA-2).
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## Notes
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The Makefile is as minimal as possible. No effort was put into making
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it general. Its purpose is mainly to ease testing for the developer's
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host machine. The actual implementation is however extremely easy to
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include in any project, may it use GNU make or any other build tool.
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## Code review
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This code has been reviewed at [Stack Exchange CODE
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REVIEW](https://codereview.stackexchange.com/questions/182812/self-contained-sha-256-implementation-in-c),
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and the implementation has been improved accordingly.
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## Testing
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Testing is continuously performed on Travis CI (see above).
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Apart from that, the implementation has been successfully tested on an x86-64 machine
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under Linux as well as on a 16-bit DSP. On the x86-64 machine, all the
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available NIST test vectors where successfully tested ([SHA-256
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examples](https://csrc.nist.gov/CSRC/media/Projects/Cryptographic-Standards-and-Guidelines/documents/examples/SHA256.pdf)
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and [SHA-2 Additional
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examples](https://csrc.nist.gov/CSRC/media/Projects/Cryptographic-Standards-and-Guidelines/documents/examples/SHA2_Additional.pdf),
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plus a few others).
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In particular:
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```
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Input Message: "abc"
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Message Digest is BA7816BF 8F01CFEA 414140DE 5DAE2223 B00361A3 96177A9C B410FF61 F20015AD
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```
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```
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Input Message: "abcdbcdecdefdefgefghfghighijhijkijkljklmklmnlmnomnopnopq"
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Message Digest is 248D6A61 D20638B8 E5C02693 0C3E6039 A33CE459 64FF2167 F6ECEDD4 19DB06C1
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```
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```
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SHA-256 Test Data
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#1) 1 byte 0xbd
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68325720 aabd7c82 f30f554b 313d0570 c95accbb 7dc4b5aa e11204c0 8ffe732b
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#2) 4 bytes 0xc98c8e55
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7abc22c0 ae5af26c e93dbb94 433a0e0b 2e119d01 4f8e7f65 bd56c61c cccd9504
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#3) 55 bytes of zeros
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02779466 cdec1638 11d07881 5c633f21 90141308 1449002f 24aa3e80 f0b88ef7
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#4) 56 bytes of zeros
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d4817aa5 497628e7 c77e6b60 6107042b bba31308 88c5f47a 375e6179 be789fbb
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#5) 57 bytes of zeros
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65a16cb7 861335d5 ace3c607 18b5052e 44660726 da4cd13b b745381b 235a1785
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#6) 64 bytes of zeros
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f5a5fd42 d16a2030 2798ef6e d309979b 43003d23 20d9f0e8 ea9831a9 2759fb4b
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#7) 1000 bytes of zeros
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541b3e9d aa09b20b f85fa273 e5cbd3e8 0185aa4e c298e765 db87742b 70138a53
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#8) 1000 bytes of 0x41 ‘A’
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c2e68682 3489ced2 017f6059 b8b23931 8b6364f6 dcd835d0 a519105a 1eadd6e4
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#9) 1005 bytes of 0x55 ‘U’
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f4d62dde c0f3dd90 ea1380fa 16a5ff8d c4c54b21 740650f2 4afc4120 903552b0
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#10) 1000000 bytes of zeros
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d29751f2 649b32ff 572b5e0a 9f541ea6 60a50f94 ff0beedf b0b692b9 24cc8025
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#11) 0x20000000 (536870912) bytes of 0x5a ‘Z’
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15a1868c 12cc5395 1e182344 277447cd 0979536b adcc512a d24c67e9 b2d4f3dd
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#12) 0x41000000 (1090519040) bytes of zeros
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461c19a9 3bd4344f 9215f5ec 64357090 342bc66b 15a14831 7d276e31 cbc20b53
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#13) 0x6000003e (1610612798) bytes of 0x42 ‘B’
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c23ce8a7 895f4b21 ec0daf37 920ac0a2 62a22004 5a03eb2d fed48ef9 b05aabea
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```
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## License
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This repository is made available under a permissive license. See
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[LICENSE FILE](LICENSE.md).
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## Reference implementation
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I had missed that when I made this implementation but [RFC 6234, chapter 8](https://tools.ietf.org/html/rfc6234#section-8) actually includes a reference implementation in C that is (at least in ambition) broader in scope than this one. I have however neither compiled nor tested it.
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