How to Generate a SHA256 HMAC Hash from a String in Go

Created Jun 23, 2022 at 10:29

Modified Jun 23, 2022 at 12:01

In cryptography, an HMAC (hash-based message authentication code) is a specific type of message authentication code (MAC) involving a cryptographic hash function and a secret cryptographic key.

Using hmac Package

The hmac.New() function returns a new HMAC hash using the given hash.Hash type and key.

The following example should cover whatever you are trying to do:

package main

import (
  "crypto/hmac"
  "crypto/sha256"
  "fmt"
)

func main() {
  s := "Hello"

  key := "FDJ1mnhuzjFjTdwhq7DtZG2Cq9kuuEZCG"
  h := hmac.New(sha256.New, []byte(key))

  h.Write([]byte(s))
  fmt.Printf("%x\n", h.Sum(nil))

  fmt.Printf("%x\n", sha256.Sum256([]byte(s)))
}

b5352927e7a57a6485fa4afa7452b3817abe47d07c8aa2511bdcb9a43ac0f224
185f8db32271fe25f561a6fc938b2e264306ec304eda518007d1764826381969

Generating a MD5 HMAC Hash

For example,

package main

import (
  "crypto/hmac"
  "crypto/md5"
  "fmt"
)

func main() {
  s := "Hello"

  key := "FDJ1mnhuzjFjTdwhq7DtZG2Cq9kuuEZCG"
  h := hmac.New(md5.New, []byte(key))

  h.Write([]byte(s))
  fmt.Printf("%x\n", h.Sum(nil))
}

ed1d2af782f2fa171867e4e810bf9a3d

block length:

Hash function H	b, bytes	L, bytes
MD5	64	16
SHA-1	64	20
SHA-224	64	28
SHA-256	64	32
SHA-512/224	128	28
SHA-512/256	128	32
SHA-384	128	48
SHA-512	128	64
SHA3-224	144	28
SHA3-256	136	32
SHA3-384	104	48
SHA3-512	72	64
out = H( in ) L = length( out ) b = H's internal block length