Ideally, a relying party that needs to verify certain attributes of a user would do so all by himself. However, in the new German eID system there are currently 7 so called eID service providers that handle this task on behalf of many relying parties. The Germans did this to allow service providers to quickly adopt the new eID system, because they can simply contract an eID service provider instead of implementing the functionality themselves. However, this creates a hotspot. For all users the eID service provider sees all attributes verified for all relying parties it services. The eID service provider is therefore in principle able to link a user to all the relying parties it visits, together with the relevant attributes. This appears to be a serious privacy risk. Or isn’t it?
In the IRMA (I Reveal My Attributes) project we are working to make attribute based credentials practical. IRMA provides very efficient implementations of such credentials on (contactless) smart cards. This allows us to use the smart card as a secure and portable container for these credentials. One of the things we have been looking at is possible use cases. Last week I discussed how the IRMA card can be used to stop the resale of event tickets. In this blog post I will discuss an almost trivial application: proving age bounds.
In the IRMA (I Reveal My Attributes) project we are working to make attribute based credentials practical. One of the things we have been looking at is possible use cases for such credentials, especially when they are implemented on a (contactless) smart card. One particularly interesting use case is the sale of tickets for events.
In this rather long post, I’d like to discuss the practical difficulty of securely collecting and combining attributes from different contexts when one starts using a system based on attribute based credentials. How do you determine that two separate contexts really belong to the same person? How do you ensure that a few people colluding cannot create a supercredential combining their individual attributes.
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I recently learnt that the new German identity card (or nPA for neuer Personalausweis has security, privacy and usability problems. This was brought to my attention during a number of discussions with experts, as well as a recent publication by a group of researcher from Frauenhofer SIT. The findings have been verified against the official documentation. The issues concern the eID application on the card that is to be used for authentication on the Internet (and not the electronic passport functionality that is also present on the same card).
Anonymous credentials are a privacy enhancing technology that allow you to prove certain properties about yourself, without revealing your full identity. Examples are showing your age, your gender, whether you are a member of a certain group, or your nationality, among others. Privacy advocates are advocating the widespread use of such technology. However, if a worldwide infrastructure for anonymous credentials would exist, this would actually create a funny privacy problem.
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In a previous blog post I argued that identity cards should not be used to store anonymous credentials. The reason being that users may not believe that a card that is used to identify them in one context, can also be used anonymously in another. But last Friday, in a meeting with Martijn Oostdijk among others, I heard an interesting reason why anonymous credentials perhaps should be stored on an identity card anyway.