# Hash algorithm analysis

*Date*: Sat, 9 Jun 2018 22:49:13 +0000*From*: "brian m. carlson" <sandals@xxxxxxxxxxxxxxxxxxxx>*Subject*: Hash algorithm analysis

== Discussion of Candidates I've implemented and tested the following algorithms, all of which are 256-bit (in alphabetical order): * BLAKE2b (libb2) * BLAKE2bp (libb2) * KangarooTwelve (imported from the Keccak Code Package) * SHA-256 (OpenSSL) * SHA-512/256 (OpenSSL) * SHA3-256 (OpenSSL) * SHAKE128 (OpenSSL) I also rejected some other candidates. I couldn't find any reference or implementation of SHA256×16, so I didn't implement it. I didn't consider SHAKE256 because it is nearly identical to SHA3-256 in almost all characteristics (including performance). I imported the optimized 64-bit implementation of KangarooTwelve. The AVX2 implementation was not considered for licensing reasons (it's partially generated from external code, which falls foul of the GPL's "preferred form for modifications" rule). === BLAKE2b and BLAKE2bp These are the non-parallelized and parallelized 64-bit variants of BLAKE2. Benefits: * Both algorithms provide 256-bit preimage resistance. Downsides: * Some people are uncomfortable that the security margin has been decreased from the original SHA-3 submission, although it is still considered secure. * BLAKE2bp, as implemented in libb2, uses OpenMP (and therefore multithreading) by default. It was no longer possible to run the testsuite with -j3 on my laptop in this configuration. === Keccak-based Algorithms SHA3-256 is the 256-bit Keccak algorithm with 24 rounds, processing 136 bytes at a time. SHAKE128 is an extendable output function with 24 rounds, processing 168 bytes at a time. KangarooTwelve is an extendable output function with 12 rounds, processing 136 bytes at a time. Benefits: * SHA3-256 provides 256-bit preimage resistance. * SHA3-256 has been heavily studied and is believed to have a large security margin. I noted the following downsides: * There's a lack of a availability of KangarooTwelve in other implementations. It may be the least available option in terms of implementations. * Some people are uncomfortable that the security margin of KangarooTwelve has been decreased, although it is still considered secure. * SHAKE128 and KangarooTwelve provide only 128-bit preimage resistance. === SHA-256 and SHA-512/256 These are the 32-bit and 64-bit SHA-2 algorithms that are 256 bits in size. I noted the following benefits: * Both algorithms are well known and heavily analyzed. * Both algorithms provide 256-bit preimage resistance. == Implementation Support |=== | Implementation | OpenSSL | libb2 | NSS | ACC | gcrypt | Nettle| CL | | SHA-1 | 🗸 | | 🗸 | 🗸 | 🗸 | 🗸 | {1} | | BLAKE2b | f | 🗸 | | | 🗸 | | {2} | | BLAKE2bp | | 🗸 | | | | | | | KangarooTwelve | | | | | | | | | SHA-256 | 🗸 | | 🗸 | 🗸 | 🗸 | 🗸 | {1} | | SHA-512/256 | 🗸 | | | | | 🗸 | {3} | | SHA3-256 | 🗸 | | | | 🗸 | 🗸 | {4} | | SHAKE128 | 🗸 | | | | 🗸 | | {5} | |=== f: future version (expected 1.2.0) ACC: Apple Common Crypto CL: Command-line :1: OpenSSL, coreutils, Perl Digest::SHA. :2: OpenSSL, coreutils. :3: OpenSSL :4: OpenSSL, Perl Digest::SHA3. :5: Perl Digest::SHA3. === Performance Analysis The test system used below is my personal laptop, a 2016 Lenovo ThinkPad X1 Carbon with an Intel i7-6600U CPU (2.60 GHz) running Debian unstable. I implemented a test tool helper to compute speed much like OpenSSL does. Below is a comparison of speeds. The columns indicate the speed in KiB/s for chunks of the given size. The runs are representative of multiple similar runs. 256 and 1024 bytes were chosen to represent common tree and commit object sizes and the 8 KiB is an approximate average blob size. Algorithms are sorted by performance on the 1 KiB column. |=== | Implementation | 256 B | 1 KiB | 8 KiB | 16 KiB | | SHA-1 (OpenSSL) | 513963 | 685966 | 748993 | 754270 | | BLAKE2b (libb2) | 488123 | 552839 | 576246 | 579292 | | SHA-512/256 (OpenSSL) | 181177 | 349002 | 499113 | 495169 | | BLAKE2bp (libb2) | 139891 | 344786 | 488390 | 522575 | | SHA-256 (OpenSSL) | 264276 | 333560 | 357830 | 355761 | | KangarooTwelve | 239305 | 307300 | 355257 | 364261 | | SHAKE128 (OpenSSL) | 154775 | 253344 | 337811 | 346732 | | SHA3-256 (OpenSSL) | 128597 | 185381 | 198931 | 207365 | | BLAKE2bp (libb2; threaded) | 12223 | 49306 | 132833 | 179616 | |=== SUPERCOP (a crypto benchmarking tool; https://bench.cr.yp.to/results-hash.html) has also benchmarked these algorithms. Note that BLAKE2bp is not listed, KangarooTwelve is k12, SHA-512/256 is equivalent to sha512, SHA3-256 is keccakc512, and SHAKE128 is keccakc256. Information is for kizomba, a Kaby Lake system. Counts are in cycles per byte (smaller is better; sorted by 1536 B column): |=== | Algorithm | 576 B | 1536 B | 4096 B | long | | BLAKE2b | 3.51 | 3.10 | 3.08 | 3.07 | | SHA-1 | 4.36 | 3.81 | 3.59 | 3.49 | | KangarooTwelve | 4.99 | 4.57 | 4.13 | 3.86 | | SHA-512/256 | 6.39 | 5.76 | 5.31 | 5.05 | | SHAKE128 | 8.23 | 7.67 | 7.17 | 6.97 | | SHA-256 | 8.90 | 8.08 | 7.77 | 7.59 | | SHA3-256 | 10.26 | 9.15 | 8.84 | 8.57 | |=== Numbers for genji262, an AMD Ryzen System, which has SHA acceleration: |=== | Algorithm | 576 B | 1536 B | 4096 B | long | | SHA-1 | 1.87 | 1.69 | 1.60 | 1.54 | | SHA-256 | 1.95 | 1.72 | 1.68 | 1.64 | | BLAKE2b | 2.94 | 2.59 | 2.59 | 2.59 | | KangarooTwelve | 4.09 | 3.65 | 3.35 | 3.17 | | SHA-512/256 | 5.54 | 5.08 | 4.71 | 4.48 | | SHAKE128 | 6.95 | 6.23 | 5.71 | 5.49 | | SHA3-256 | 8.29 | 7.35 | 7.04 | 6.81 | |=== Note that no mid- to high-end Intel processors provide acceleration. AMD Ryzen and some ARM64 processors do. == Summary The algorithms with the greatest implementation availability are SHA-256, SHA3-256, BLAKE2b, and SHAKE128. In terms of command-line availability, BLAKE2b, SHA-256, SHA-512/256, and SHA3-256 should be available in the near future on a reasonably small Debian, Ubuntu, or Fedora install. As far as security, the most conservative choices appear to be SHA-256, SHA-512/256, and SHA3-256. The performance winners are BLAKE2b unaccelerated and SHA-256 accelerated. -- brian m. carlson: Houston, Texas, US OpenPGP: https://keybase.io/bk2204

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**Follow-Ups**:**Re: Hash algorithm analysis***From:*Ævar Arnfjörð Bjarmason

**Re: Hash algorithm analysis***From:*Jonathan Nieder

**References**:**State of NewHash work, future directions, and discussion***From:*brian m. carlson

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