Interchangeably use RSA & ECDSA with PEM and JWK for Signing, Verifying, CSR generation and JOSE. Ugh... that was a mouthful. :)
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Lightweight JavaScript RSA and ECDSA utils that work on Windows, Mac, and Linux using modern node.js APIs (no need for C compiler).

A thin wrapper around Eckles.js (ECDSA) and Rasha.js (RSA).



A brief (albeit somewhat nonsensical) introduction to the APIs:

Keypairs.generate().then(function (pair) {
  return Keypairs.export({ jwk: pair.private }).then(function (pem) {
    return Keypairs.import({ pem: pem }).then(function (jwk) {
      return Keypairs.thumbprint({ jwk: jwk }).then(function (thumb) {
        return Keypairs.signJwt({
          jwk: keypair.private
        , claims: {
            iss: ''
          , sub: ''
          , exp: Math.round( + (3 * 24 * 60 * 60)

By default ECDSA keys will be used since they’ve had native support in node much longer than RSA has, and they’re smaller, and faster to generate.

API Overview

  • generate
  • parse
  • parseOrGenerate
  • import (PEM-to-JWK)
  • export (JWK-to-PEM, private or public)
  • publish (Private JWK to Public JWK)
  • thumbprint (JWK SHA256)
  • signJwt
  • signJws


Generates a public/private pair of JWKs as { private, public }

Option examples:

  • RSA { kty: 'RSA', modulusLength: 2048 }
  • ECDSA { kty: 'ECDSA', namedCurve: 'P-256' }

When no options are supplied EC P-256 (also known as prime256v1 and secp256r1) is used by default.


Parses either a JWK (encoded as JSON) or an x509 (encdode as PEM) and gives back the JWK representation.

Option Examples:

  • JWK { key: ‘{ “kty”:“EC”, ... }’ }
  • PEM { key: ‘-----BEGIN PRIVATE KEY-----\n...’ }
  • Public Key Only { key: ‘-----BEGIN PRIVATE KEY-----\n...', public: true }
  • Must Have Private Key { key: ‘-----BEGIN PUBLIC KEY-----\n...', private: true }


Keypairs.parse({ key: '...' }).catch(function (e) {
  // could not be parsed or was a public key
  return Keypairs.generate();

Keypairs.parseOrGenerate({ key, throw, [generate opts]... })

Parses the key. Logs a warning on failure, marches on. (a shortcut for the above, with private: true)

Option Examples:

  • parse key if exist, otherwise generate { key: process.env["PRIVATE_KEY"] }
  • generated key curve { key: null, namedCurve: 'P-256' }
  • generated key modulus { key: null, modulusLength: 2048 }


Keypairs.parseOrGenerate({ key: process.env["PRIVATE_KEY"] }).then(function (pair) {

Great for when you have a set of shared keys for development and randomly generated keys in

Keypairs.import({ pem: ‘...’ }

Takes a PEM in pretty much any format (PKCS1, SEC1, PKCS8, SPKI) and returns a JWK.


Exports a JWK as a PEM.

Exports PEM in PKCS8 (private) or SPKI (public) by default.


{ jwk: jwk
, public: true
, encoding: 'pem' // or 'der'
, format: 'pkcs8' // or 'ssh', 'pkcs1', 'sec1', 'spki'

Keypairs.publish({ jwk: jwk })

Synchronously strips a key of its private parts and returns the public version.

Keypairs.thumbprint({ jwk: jwk })

Promises a JWK-spec thumbprint: URL Base64-encoded sha256

Keypairs.signJwt({ jwk, header, claims })

Returns a JWT (otherwise known as a protected JWS in “compressed” format).

{ jwk: jwk
, claims: {

Header defaults:

{ kid: thumbprint
, alg: 'xS256'
, typ: 'JWT'

Payload notes:

  • iat: now is added by default (set false to disable)
  • exp must be set (set false to disable)
  • iss should be the base URL for JWK lookup (i.e. via OIDC, Auth0)


header is actually the JWS protected value, as all JWTs use protected headers (yay!) and claims are really the JWS payload.

Keypairs.signJws({ jwk, header, protected, payload })

This is provided for APIs like ACME (Let’s Encrypt) that use uncompressed JWS (instead of JWT, which is compressed).


  • header not what you think. Leave undefined unless you need this for the spec you’re following.
  • protected is the typical JWT-style header
    • kid and alg will be added by default (these are almost always required), set false explicitly to disable
  • payload can be JSON, a string, or even a buffer (which gets URL Base64 encoded)
    • you must set this to something, even if it’s an empty string, object, or Buffer

Additional Documentation

Keypairs.js provides a 1-to-1 mapping to the Rasha.js and Eckles.js APIs for the following:

  • generate(options)
  • import({ pem: ‘---BEGIN...’ })
  • export({ jwk: { kty: ‘EC’, ... })
  • thumbprint({ jwk: jwk })

If you want to know the algorithm-specific options that are available for those you’ll want to take a look at the corresponding documentation: