asn1.js

What is asn1.js?

The asn1.js package is a library designed to provide Abstract Syntax Notation One (ASN.1) parsing and encoding capabilities in JavaScript. It's particularly useful for dealing with cryptographic data formats and protocols, allowing developers to encode and decode data in a standardized format.

What are asn1.js's main functionalities?

ASN.1 DER Encoding

This feature allows for the encoding of ASN.1 data types into Distinguished Encoding Rules (DER) format. The code sample demonstrates how to define an ASN.1 integer and encode it into DER format.

const ASN1 = require('asn1.js');

const ASN1Integer = ASN1.define('ASN1Integer', function() {
  this.int();
});

const encoded = ASN1Integer.encode(123, 'der');

ASN.1 DER Decoding

This feature enables the decoding of ASN.1 data encoded in DER format back into its original form. The code sample shows how to decode a previously encoded ASN.1 integer.

const ASN1 = require('asn1.js');

const ASN1Integer = ASN1.define('ASN1Integer', function() {
  this.int();
});

const decoded = ASN1Integer.decode(encoded, 'der');

Other packages similar to asn1.js

node-forge

node-forge is a comprehensive Node.js library that provides a wide range of cryptographic functionalities, including ASN.1 parsing and encoding. Compared to asn1.js, node-forge offers a broader set of cryptographic tools but might be more complex to use for ASN.1 specific tasks.

pkijs

pkijs is a pure JavaScript library that provides a high-level interface to work with PKI (Public Key Infrastructure) and ASN.1. It is more focused on PKI and related standards, making it a good choice for applications dealing with X.509 certificates or CMS (Cryptographic Message Syntax). While it includes ASN.1 functionality, it is part of a larger suite of PKI-related features.

README

ASN1.js

ASN.1 DER Encoder/Decoder and DSL.

Example

Define model:

var asn = require('asn1.js');

var Human = asn.define('Human', function() {
  this.seq().obj(
    this.key('firstName').octstr(),
    this.key('lastName').octstr(),
    this.key('age').int(),
    this.key('gender').enum({ 0: 'male', 1: 'female' }),
    this.key('bio').seqof(Bio)
  );
});

var Bio = asn.define('Bio', function() {
  this.seq().obj(
    this.key('time').gentime(),
    this.key('description').octstr()
  );
});

Encode data:

var output = Human.encode({
  firstName: 'Thomas',
  lastName: 'Anderson',
  age: 28,
  gender: 'male',
  bio: [
    {
      time: +new Date('31 March 1999'),
      description: 'freedom of mind'
    }
  ]
}, 'der');

Decode data:

var human = Human.decode(output, 'der');
console.log(human);
/*
{ firstName: <Buffer 54 68 6f 6d 61 73>,
  lastName: <Buffer 41 6e 64 65 72 73 6f 6e>,
  age: 28,
  gender: 'male',
  bio:
   [ { time: 922820400000,
       description: <Buffer 66 72 65 65 64 6f 6d 20 6f 66 20 6d 69 6e 64> } ] }
*/

Partial decode

Its possible to parse data without stopping on first error. In order to do it, you should call:

var human = Human.decode(output, 'der', { partial: true });
console.log(human);
/*
{ result: { ... },
  errors: [ ... ] }
*/

LICENSE

This software is licensed under the MIT License.

Copyright Fedor Indutny, 2017.

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.