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Mar 31, 2022
Aug 27, 2020

Smart Card Browser Extension

This smart card browser extension is an attempt to provide a bridge between the JavaScript world that a Web developer is familiar with and the native smart card subsystems available in PC platforms.

The idea is that a Web developer who wants to have low level access to smart cards in the machine where the browser is running would add a webcard.js file to the page. That script would in turn check if the extension is installed and if not prompt the user to install it.

The extension adds a webcard object to navigator and through it navigator.webcard.readers provides a list of the smart card reader objects available in the machine. Each reader has a name and an atr if there is a card inserted on it.

reader has three methods:

  • connect to establish a connection with the inserted card. It receives an optional argument to indicate if the connection should be exclusive or not (shared) the default is true
  • transcieve that sends the APDU passed as a hexidecimal string and returs the response also as a hexadecimal string
  • disconnect closes the connection


Currently this development version requires manual installation of the unpacked extension:

  1. Build the native client for your platfrom, running either make (macOS) or MSBuild webcard.vcxproj (Windows) in the native folder
  2. Install the native client running (macOS) or install.bat (Windows) in the native folder
  3. Open Chrome -> Extensions, enable developer mode and add the unpacked extension from the extension folder.
  4. Open the test page, for example running python3 -m http.server from the test folder and then navigate to http://localhost:8000

Native Messages

Messages to native:

{i: 'string', c: integer, r: integer, a: 'string', p: integer}

i: unique message identifier c: command 1-list readers, 2-connect, 3-disconnect, 4-transcieve r: index of reader in reader list a: hex cAPDU to send to the card, sent only for c: 4 p: parameter, share mode for connect, sent only for c: 2

Messages from native:

{i: 'string', e: integer, r: integer, d: [array]|'string'}

i: unique message identifier, to link the response. Empty string on reader events e: reader event 1-card insert, 2-card remove. Sent only for reader events r: reader index for reader events d: data 1-string array with list of readers, 2-card atr, 4-hex rAPDU


There are apparently many options for smart card extensions in the Chrome store. But I could not figure out how to use them for raw APDU exchange. Maybe one of those is more suitable for your project.