Address-based identities versus Card-based identities

I was reading this blog entry about address-based identities versus card-based identities. I am still thinking about the contents and will post some more thoughts about that blog in the next few days. There was however one example in the blog I would like to comment on right away:

Whatsmore, both address-based identity and card-based identity can be further classified in some very helpful ways:

  • Address-based identities can be broken into resolvable and non-resolvable. While an address-based identity is always unique in the address space in which it is assigned, that doesn’t necessarily mean it can be resolved, i.e., dereferenced via a mechanism or protocol that provides further discover or communications with a digital subject. An email address is a good example of the former; a browser cookie a good example of the latter.
  • Card-based identities can be broken into addressable and non-addressable. This means that some card-based identities may contain an address-based identity and some may not. A business card is the classic example of an addressible card-based identity; in fact the primary purpose of most business cards is to share address-based identities. On the other hand a coffee-shop loyalty card is a good example of a non-addressable card-based identity: while it describes identity-related attributes of its owner (how many cups of coffee they have purchased), it may not contain any address-based identity whatsoever (not even your real-world name).

In the second bullet a coffee-shop loyalty card is used as an example of a card-based identity. That confuses me. Assuming, from the example, that the card does not contain any personal information like name or address, how can it be seen as a card-based identity? The only connection this loyalty card has with a person (identity) is that it is carried around by one. But that would make a lot of items suddenly card-based identities. The card cannot be used to identify or authenticate a person and has only value to the person carrying it around but it is in no way connected to that person. Following this reasoning, the 10 EURO note I am carrying around also is a card-based identity.


1 thought on “Address-based identities versus Card-based identities

  1. The coffee-shop loyalty card is an identity. The coffee-shop can build a profile of your purchasing habits over time. Sure, it’s identified as ‘74382432’ rather than ‘Joe Schmoe’, but it’s still your coffee habit.

    And it’s easy for the coffee shop to link ‘74382432’ to ‘Joe Schmoe’ – they could encourage you to register your card online in return for free coffee; alternatively, they can just read your name off your credit/debit card the first time you use it to pay for coffee…


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