How to generate HMAC-SHA-256 sign in javascript for datatrans?

Question

I have an Angular project in which I have to implement datatrans payment. But I am not able to generate sign for payment.

I am following process given on this link (enter link description here) to generate sign.

But i am not able to achive it.

I am using angular library crypto-js to generate HMAC-SHA-256 signed string.

Here is my javascript code.

const merchantId = 'xxxxxxx';
const refNo = '1234567890';
const amount = 0;
const currency = 'CHF';
const theme = 'DT2015';
const paymentmethod = 'VIS';

const stringSs = merchantId+amount+currency+refNo;

const base = 16;
// My Hmac Key
const s = 'fa3d0ea1772cf21e53158283e4f123ebf1eb1ccfb15619e2fc91ee6860a2e5e48409e902b610ce5dc6f7f77fab8affb60d69b2a7aa9acf56723d868d36ab3f32';

// Step 1: Code to generate hex to byte of hmac key
const a = s.replace(/../g, '$&_').slice (0, -1).split ('_').map ((x) => parseInt (x, base));

//  Step 3: Sign the string with HMAC-SHA-256 together with your HMAC key
const signedString = HmacSHA256(a, stringSs);

// Step 4: Translate the signature from byte to hex format
const signString = enc.Hex.stringify(signedString);

Can you help me into this to suggest what i am doing wrong or in what way it can be achieved.

Luca · Accepted Answer · 2020-11-10 09:38:19Z

11

You can do it with crypto (no need of extra libraries to install)

// Typescript
import * as crypto from 'crypto';

function signKey (clientKey: string, msg: string) {
    const key = new Buffer(clientKey, 'hex');
    return crypto.createHmac('sha256', key).update(msg).digest('hex');
}

// Javascript
const crypto = require('crypto')

function signKey (clientKey, msg) {
    const key = new Buffer(clientKey, 'hex');
    return crypto.createHmac('sha256', key).update(msg).digest('hex');
}

signKey(s, stringSs)

answered Nov 10, 2020 at 9:38

Luca

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Comments

Friggens · Accepted Answer · 2022-09-10 10:34:50Z

To answer the question for crypto-js (see https://github.com/brix/crypto-js) as requested, the following will do the trick:

// Javascript; example from datatrans documentation using a random key
stringSs ='3000017692850CHF91827364';
key='1ca12d7c0629194a9f9d0dbbc957709dd3aed385925b077e726813f0b452de6a38256abd1116138d21754cfb33964b6b1aaa375b74d3580fcda916898f553c92';
expectedSign='d7dee9ae1e542bc02bcb063a3dd3673871b2e43ccb4c230f26e8b85d14e25901';

signedString = CryptoJS.HmacSHA256(stringSs, CryptoJS.enc.Hex.parse(key));
resultSign = CryptoJS.enc.Hex.stringify(signedString);

// now resultSign == expectedSign is true :-)

Ninja Turtles approach was almost correct except of step 1, hex to byte. Use a builtin function of Crypto-JS instead and everything works as expected.

Andrew E · Accepted Answer · 2024-04-17 15:39:38Z

1

Modern browsers have crypto built in, no npm modules required,

Here's a rough TypeScript implementation, borrowing heavily from https://developer.mozilla.org/en-US/docs/Web/API/SubtleCrypto/digest (I expect this could be improved):

async function signString(s: string): Promise<string> {
  const msgUint8 = new TextEncoder().encode(s)
  const buf = await crypto.subtle.digest('SHA-256', msgUint8)
  const hashArray = Array.from(new Uint8Array(buf))
  return hashArray.map(b => b.toString(16).padStart(2, '0')).join(''))
}

answered Apr 17, 2024 at 15:39

Andrew E

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