A smart card is a device that holds a private key securely without letting it out of its storage. The chip on your credit card is a “smart card” (yup, terminology is ambiguous – the card and the chip are interchangeably called “smart card”). There are smaller USB-pluggable hardware readers that only hold the chip (without an actual card – e.g. this one).
But what’s the use? This w3c workshop from several years ago outlines some of them: multi-factor authentication, state-accepted electronic identification, digital signatures. All these are part of a bigger picture – that using the internet is now the main means of communication. We are moving most of our real-world activities online, so having a way to identify who we are online (e.g. to a government, to a bank), or being able to sign documents online (with legal value) is crucial.
That’s why the EU introduced the eIDAS regulation which defines (among other things) electronic identification and digital signatures. The framework laid there is aimed at having legally binding electronic communication, which is important in so many cases. Have you ever done the print-sign-scan exercise? Has your e-banking been accessed by an unauthorized person? Well, the regulation is supposed to fix these and more more issues.
Two factor authentication is another more broad concept, which has a tons of sub-optimal solutions. OTP tokens, google authenticator, sms code confirmation. All these have issues (e.g. clock syncing, sms interception, cost). There are hardware tokens like YubiKey, but they offer only a subset of the features a smart card does.
But it’s not just about legally-recognized actions online and two-factor authentication. It opens up other possibilities, like a more secure online credit card payment – e.g. you put your card in a reader and type your PIN, rather than entering the card number, CVC, date, names, 3d password and whatnot.
With this long introduction I got to the problem: browsers don’t support smart cards. In the EU, where electronic signatures are legally recognized, there is always the struggle of making them work with browsers. The solution so far: Java applets. A Java applet can interact with the smart card through the java crypto APIs, and thus provide signing features. However, with the deprecation of Java applets this era of constant struggle will end soon (and it is a struggle – having to click at least 2 confirmations and keep your java up to date, which even for developers is a hassle). There used to be a way to do it a few years ago in Firefox and IE, using window.crypto and CAPICOM APIs, but these got deprecated.
Recently the trend has been to use a “cloud-based” approach, where the keys reside on an HSM. That’s of course useful, but the problem with identification remains – getting access to your keys on the HSM requires, again, two factor authentication. Having the hardware token “in your hands” is what adds the security.
Smart people in Estonia (which has the most digital government in the world) had a better solution than Java or HSM – browser plugins that allow interaction with their ID card (which is/has a smart card). The solution is here and here. This has worked pretty well – you install the plugins one (which a one-in-all installer) and you can sign documents with javascript. You also get the proper PKCS libraries installed, and the root certificates needed to allow TLS 1.2 authentication with the hardware token (identification and authentication vs signing). The small downside of this approach is that it is somewhat fragile and dependent on browser whims – the plugins have to be upgraded constantly and are at risk of being completely broken if some browser decides to deprecate some Plugin APIs.
Another approach is the “local service” approach, which has two flavours. One is – you install a local application that exposes an HTTP interface and using javascript and proper same-origin configuration you send the files needed for signing to the service, and then get the result as an HTTP response, which you can then, again using javascript, append to the page that requested the signing. The downside here – getting a service installed to listen to a given port without administrator rights. The other approach is having an application hooked to a custom protocol (e.g. signature://). So whenever the page wants the user to sign something, it opens signnature://path-to-document-to-sign, which is intercepted by the locally installed application, digital signing is performed, and the result is pushed to (one-time) URL specified in the metadata of the document to sign. Something like that is implemented by 4identity.eu and it actually works.
Now, signature is one thing, identification (TLS client auth) is another. Allegedly, things should work there – PKCS#11 is a standard that should allow TLS client auth to happen with a smart card. Reality is – it doesn’t. You often need a vendor-specific PKCS#11 library. OpenSC, which is a cool tool that works with many smart cards, only works with Firefox and Safari. Charismatics commercial is a piece of software that is supposed to work with all smart cards out there – well, it doesn’t always.
And the problem here is the smart card vendors. The need for OpenSC and Charismatics arises because even though there are a few PKCS standards, smart cards are a complete mess. Not only it’s a mess, but it’s a closed, secretive mess. APDUs (the commands you send to the smartcard in order to communicate with it) are in most cases secret. You don’t get to know them even if you purchase tens of thousands of cards – you only get a custom vendor software that knows them. Then you have to reverse-engineer them to know how to actually talk to them. And they differ not only across vendors, but across card models of different vendors. For that reason the Estonian approach was a bit simpler to implement – they had only one type of smart card, given to all citizens and they were mostly in control. In other countries it’s a … mess. At least a dozen different types of cards to be supported.
So my first request is to smart card vendors (which are not that many) – please, please fix your mess. Get rid of that extra bit of “security through obscurity” to allow browsers to communicate with you without extra shenanigans.
My second request is to browser vendors – please do support smart card crypto natively. Unfortunately, due to the smart card mess above (among other things), hardware crypto has explicitly been excluded from the Web crypto API. As a follow-up to that, there’s the Hardware security working group, but afaik it’s still “work in progress”, and my feeling is it’s not that much yet. In w3c it’s important that browser vendors agree to implement something before it’s a standard, and I’ve heard that some are opposing the smart card integration. Due to the aforementioned mess, I guess.
You may say – standardization will fix this. Well, it hasn’t so far. The EU officials are aware of the problem, and that the eIDAS regulation may be thwarted by these technical issues, but they are powerless, as the EU is not a standardization body.
So it all comes down to having a joint effort between browser and smart card vendors to fix this thing once and for all. So, please do that in order to enable a more secure and legally-compliant web.
| Reference: | A Case For Native Smart Card Support in Browsers from our JCG partner Bozhidar Bozhanov at the Bozho’s tech blog blog. |
