:: a typeCtrl KGHC 9.10.3 · lts/ghc-9.10.x · 248f8f0 · 2026-10-05
Modulecryptohash-sha256-0.11.102.1Haskell2010
A module containing SHA-256 bindings
This API is based on 4 different functions, similar to the lowlevel operations of a typical hash:
init: create a new hash context
update: update non-destructively a new hash context with a strict bytestring
updates: same as update, except that it takes a list of strict bytestrings
finalize: finalize the context and returns a digest bytestring.
all those operations are completely pure, and instead of changing the context as usual in others language, it re-allocates a new context each time.
Example:
import qualified Data.ByteString
import qualified Crypto.Hash.SHA256 as SHA256
main = print digest
where
digest = SHA256.finalize ctx
ctx = foldl SHA256.update ctx0 (map Data.ByteString.pack [ [1,2,3], [4,5,6] ])
ctx0 = SHA256.initSHA-256 Context
The context data is exactly 104 bytes long, however the data in the context is stored in host-endianness.
The context data is made up of
a Word64 representing the number of bytes already feed to hash algorithm so far,
a 64-element Word8 buffer holding partial input-chunks, and finally
a 8-element Word32 array holding the current work-in-progress digest-value.
Consequently, a SHA-256 digest as produced by hash, hashlazy, or finalize is 32 bytes long.
create a new hash context
update a context with a bytestring
updates a context with multiple bytestrings
finalize the context into a digest bytestring (32 bytes)
Variant of finalize also returning length of hashed content
hash a strict bytestring into a Ctx
hash a lazy bytestring into a Ctx
This API use the incremental API under the hood to provide the common all-in-one operations to create digests out of a ByteString and lazy ByteString.
hash: create a digest (init + update + finalize) from a strict ByteString
hashlazy: create a digest (init + update + finalize) from a lazy ByteString
hashlazyAndLength: create a digest (init + update + finalizeAndLength) from a lazy ByteString
Example:
import qualified Data.ByteString
import qualified Crypto.Hash.SHA256 as SHA256
main = print $ SHA256.hash (Data.ByteString.pack [0..255])NOTE: The returned digest is a binary ByteString. For converting to a base16/hex encoded digest the base16-bytestring package is recommended.
hash a strict bytestring into a digest bytestring (32 bytes)
hash a lazy bytestring into a digest bytestring (32 bytes)
Variant of hashlazy which simultaneously computes the hash and length of a lazy bytestring.
Compute 32-byte RFC2104-compatible HMAC-SHA-256 digest for a strict bytestring message
Compute 32-byte RFC2104-compatible HMAC-SHA-256 digest for a lazy bytestring message
hmaclazyAndLength :: ByteStringsecret
-> ByteStringmessage
-> (ByteString, Word64)digest (32 bytes) and length of message
Variant of hmaclazy which also returns length of message
hkdf :: ByteStringIKM Input keying material
-> ByteStringsalt Optional salt value, a non-secret random value (can be "")
-> ByteStringinfo Optional context and application specific information (can be "")
-> IntL length of output keying material in octets (at most 255*32 bytes)
-> ByteStringOKM Output keying material (L bytes)
RFC6234-compatible HKDF-SHA-256 key derivation function.