sha2

nimony/lib/std/crypto/sha2.nim

SHA-2 (FIPS 180-4): SHA-256, SHA-384 and SHA-512.

SHA-256 is the transcript hash and the HKDF hash of the TLS 1.3 suites std/tls speaks; SHA-384 and SHA-512 are what certificate signatures are computed over. None of them branches on or indexes by the data, so the straightforward implementation is already constant time.

type Sha256Digest = array[0..31, uint8]
type Sha384Digest = array[0..47, uint8]
type Sha512Digest = array[0..63, uint8]

type Sha256 = object
  h: array[0..7, uint32]
  buf: array[0..63, uint8]
  bufLen: 0..63
  total: uint64

type Sha512 = object
  h: array[0..7, uint64]
  buf: array[0..127, uint8]
  bufLen: 0..127
  total: uint64

func initSha256(): Sha256
func update(s: var Sha256; data: openArray[uint8])
func update(s: var Sha256; data: string)
func finish(s: Sha256): array[0..31, uint8]
The digest of everything fed so far. s is not consumed — that is what lets a TLS transcript hash be read and then extended.
func sha256(data: openArray[uint8]): array[0..31, uint8]
func sha256(data: string): array[0..31, uint8]
func initSha512(): Sha512
func initSha384(): Sha512
SHA-384 is SHA-512 from another starting point, truncated; feed it with update and read it with finish384.
func update(s: var Sha512; data: openArray[uint8])
func update(s: var Sha512; data: string)
func finish(s: Sha512): array[0..63, uint8]
func finish384(s: Sha512): array[0..47, uint8]
func sha512(data: openArray[uint8]): array[0..63, uint8]
func sha384(data: openArray[uint8]): array[0..47, uint8]
func sha512(data: string): array[0..63, uint8]
func sha384(data: string): array[0..47, uint8]
func toHex(d: openArray[uint8]): string
Lower-case hex, the way digests are written in test vectors.