A pure Haskell implementation of SHA-256 and HMAC-SHA256 on strict and lazy ByteStrings, as specified by RFC's 6234 and 2104.
A sample GHCi session:
> :set -XOverloadedStrings
>
> -- import qualified
> import qualified Crypto.Hash.SHA256 as SHA256
>
> -- 'hash' and 'hmac' operate on strict bytestrings
>
> let hash_s = SHA256.hash "strict bytestring input"
> let hmac_s = SHA256.hmac "strict secret" "strict bytestring input"
>
> -- 'hash_lazy' and 'hmac_lazy' operate on lazy bytestrings
> -- but note that the key for HMAC is always strict
>
> let hash_l = SHA256.hash_lazy "lazy bytestring input"
> let hmac_l = SHA256.hmac_lazy "strict secret" "lazy bytestring input"
>
> -- results are always unformatted 256-bit (32-byte) strict bytestrings
>
> import qualified Data.ByteString as BS
>
> BS.take 10 hash_s
"1\223\152Ha\USB\171V\a"
> BS.take 10 hmac_l
"\DELSOk\180\242\182'v\187"
>
> -- you can use third-party libraries for rendering if needed
> -- e.g., using ppad-base16:
>
> import qualified Data.ByteString.Base16 as B16
>
> B16.encode hash_s
"31df9848611f42ab5607ea9e6de84b05d5259085abb30a7917d85efcda42b0e3"
> B16.encode hmac_l
"7f534f6bb4f2b62776bba3d6466e384505f2ff89c91f39800d7a0d4623a4711e"
Haddocks (API documentation, etc.) are hosted at docs.ppad.tech/sha256.
The aim is best-in-class performance for pure, highly-auditable Haskell code.
Current benchmark figures on my mid-2020 MacBook Air look like (use
cabal bench to run the benchmark suite):
benchmarking ppad-sha256/SHA256 (32B input)/hash
time 1.387 μs (1.365 μs .. 1.409 μs)
0.999 R² (0.998 R² .. 1.000 R²)
mean 1.386 μs (1.378 μs .. 1.399 μs)
std dev 34.07 ns (24.55 ns .. 52.14 ns)
variance introduced by outliers: 31% (moderately inflated)
benchmarking ppad-sha256/HMAC-SHA256 (32B input)/hmac
time 5.618 μs (5.564 μs .. 5.681 μs)
0.999 R² (0.999 R² .. 1.000 R²)
mean 5.648 μs (5.603 μs .. 5.697 μs)
std dev 159.1 ns (130.7 ns .. 194.1 ns)
variance introduced by outliers: 34% (moderately inflated)
Compare this to Hackage's famous SHA package:
benchmarking ppad-sha256/SHA256 (32B input)/SHA.sha256
time 2.585 μs (2.565 μs .. 2.613 μs)
0.999 R² (0.999 R² .. 1.000 R²)
mean 2.635 μs (2.616 μs .. 2.654 μs)
std dev 68.00 ns (58.45 ns .. 80.94 ns)
variance introduced by outliers: 32% (moderately inflated)
benchmarking ppad-sha256/HMAC-SHA256 (32B input)/SHA.hmacSha256
time 9.672 μs (9.533 μs .. 9.810 μs)
0.998 R² (0.998 R² .. 0.999 R²)
mean 9.715 μs (9.608 μs .. 9.858 μs)
std dev 394.7 ns (315.3 ns .. 576.2 ns)
variance introduced by outliers: 50% (moderately inflated)
Or the relevant SHA-256-based functions from a library with similar aims, noble-hashes:
SHA256 32B x 420,875 ops/sec @ 2μs/op ± 1.33% (min: 1μs, max: 3ms)
HMAC-SHA256 32B x 97,304 ops/sec @ 10μs/op
When reading a 1GB input from disk and testing it with hash_lazy, we
get statistics like the following:
2,310,899,616 bytes allocated in the heap
93,800 bytes copied during GC
78,912 bytes maximum residency (2 sample(s))
35,776 bytes maximum slop
10 MiB total memory in use (0 MiB lost due to fragmentation)
Tot time (elapsed) Avg pause Max pause
Gen 0 295 colls, 0 par 0.007s 0.008s 0.0000s 0.0001s
Gen 1 2 colls, 0 par 0.000s 0.001s 0.0004s 0.0004s
INIT time 0.003s ( 0.003s elapsed)
MUT time 22.205s ( 22.260s elapsed)
GC time 0.007s ( 0.009s elapsed)
EXIT time 0.000s ( 0.001s elapsed)
Total time 22.216s ( 22.273s elapsed)
%GC time 0.0% (0.0% elapsed)
Alloc rate 104,073,382 bytes per MUT second
Productivity 100.0% of total user, 99.9% of total elapsed
SHA.sha256 gets more like:
74,403,596,936 bytes allocated in the heap
12,971,992 bytes copied during GC
79,176 bytes maximum residency (2 sample(s))
35,512 bytes maximum slop
6 MiB total memory in use (0 MiB lost due to fragmentation)
Tot time (elapsed) Avg pause Max pause
Gen 0 17883 colls, 0 par 0.103s 0.148s 0.0000s 0.0001s
Gen 1 2 colls, 0 par 0.000s 0.000s 0.0002s 0.0003s
INIT time 0.006s ( 0.006s elapsed)
MUT time 32.367s ( 32.408s elapsed)
GC time 0.104s ( 0.149s elapsed)
EXIT time 0.000s ( 0.001s elapsed)
Total time 32.477s ( 32.563s elapsed)
%GC time 0.0% (0.0% elapsed)
Alloc rate 2,298,740,250 bytes per MUT second
Productivity 99.7% of total user, 99.5% of total elapsed
This library aims at the maximum security achievable in a garbage-collected language under an optimizing compiler such as GHC, in which strict constant-timeness can be challenging to achieve.
The HMAC-SHA256 functions within pass all Wycheproof vectors, as well as various other useful unit test vectors found around the internet.
If you discover any vulnerabilities, please disclose them via [email protected].
You'll require Nix with flake support enabled. Enter a development shell with:
$ nix develop
Then do e.g.:
$ cabal repl ppad-sha256
to get a REPL for the main library.
This implementation has benefitted immensely from the SHA package available on Hackage, which was used as a reference during development. Many parts wound up being direct translations.