Node.js module for NemID authentication and signing
Last updated 4 months ago by emilbayes .
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$ cnpm install nemid 
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Node.js module for NemID authentication and signing



const NemID = require('nemid')
const fs = require('fs')
const path = require('path')
const crypto = require('crypto')

// Example origin
const ORIGIN = 'https://localhost:8080'

// Paths to keys and certificates
const cert = path.join(__dirname, 'cert.der')
const key = path.join(__dirname, 'key.pem')
const issuer = path.join(__dirname, 'issuer.der')

const nemid = new NemID({
  clientKey: crypto.createPrivateKey({
    key: fs.readFileSync(key),
    format: 'pem',
    type: 'pkcs1'
  clientCert: fs.readFileSync(cert),
  serverCA: fs.readFileSync(issuer)

server.get('/authenticate', (req, res) => {
  return res.send(nemid.authenticate({ origin: ORIGIN }))
})'/authenticate/verify', (req, res) => {
  const response = req.body

  nemid.verifyAuthenticate(response, function (err, userInfo) {
    if (err) {
      // err is a NemIDError
      // Log the cause of the error on the server somehow
      // And send a user message to the client
      return res.send(err.userMessage.da)

    if (userInfo === false) {
      return res.send({ success: false })

    // Can do stuff with userInfo now
    console.log(userInfo.serialNumber) // contains the user PID

    return res.send({ success: true })


const nemid = require('nemid')
const { data: parameters } = await get('http://localhost:8080/authenticate')

const context = nemid(parameters)


const result = await context.done;

const { data: success } = await post('http://localhost:8080/authenticate/verify', result)

Server API

const nemid = new NemID({ spid, clientKey, clientCert, serverCA, env = NemID.TEST })

Create a new NemID instance. Takes 3 arguments:

  • spid is the Service Provider ID, provided by Nets at registration.
  • clientKey must be the client private key provided by Nets. See the section below for how to extract the key from the service provider bundle.
  • clientCert must be the client certificate, including intermediate certs. See the section below for how to extract this from the service provider bundle.
  • serverCA must be the Nets root certificate. This can be downloaded from NemIDs website.
  • env is an object of endpoints for the different environments. Comes with NemID.TEST and NemID.PROD built in.

const parameters = nemid.authenticate({ origin })

Create a new authentication attempt, by generating the appropriate parameters to be passed to the client side script.

nemid.verifyAuthenticate(response, cb(err, userInfo))

Verify the response from the NemID applet. May call back with an error if the result was malformed or an error code from NemID. Otherwise calls back with false for an invalid attempt or a object describing the authenticated user.

nemid.matchCPR(pid, cpr, cb(err, valid))

Verify whether pid and cpr refer to the same person.

Client API

const context = nemId(parameters, prod = false)

Initialise a new NemID authentication context with parameters from the Server API and which origin frame to load. Defaults to test ( Returns a context containing { element, done }.

const iframeElm = context.element

HTMLIFrameElement that you can place in the DOM.

const result = await context.done

Wait for the authentication to be done. Rejects in case of unexpected failure or resolves when there's a reply from NemID (which might not be a successful auth).


The element can be targeted by the CSS class nemid-iframe. Below is the default styling from NemID:

.nemid-iframe {
  border: 0;
  width: 320px;
  height: 480px;

Working with .p12

To extract all certificates, and print them to stdout:

openssl pkcs12 -in bundle.p12 -nokeys

Find you company certificate, and copy -----BEGIN CERTIFICATE----- to -----END CERTIFICATE----- inclusive and paste into a new file, eg cert.pem. This file is now in PEM format, but Nets requires it to be in DER format. It can be converted with:

openssl x509 -inform pem -outform der -text -in cert.pem -out cert.der

The remaining certificates from the first command were part of the certificate chain and need to be placed in their own file. Start by copying the sections including the start and end markers to their own file, eg. issuer.pem. Then convert them to DER format with:

openssl x509 -inform pem -outform der -text -in issuer.pem -out issuer.der

To extract the private key:

openssl pkcs12 -in bundle.p12 -nocerts -nodes

And copy the output including the start and end markers -----BEGIN PRIVATE KEY----- and -----END PRIVATE KEY----- to key.pem. This file does not need to be converted to DER format.

Note -nodes removes the passphrase from the private key. If you want to keep this, remove the option and supply your passphrase to crypto.createPrivateKey


npm install nemid



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