Friday, March 24, 2006

A Little Security Protocol puzzle

As Bruce Schneier is always talking about, sometimes real world security protocols are far more flawed and hackable than computer ones. Sometimes they are plain badly designed. And sometimes they are well designed, but reveal more about a companies priorities than they intend to.

Before I went on holiday, I went to get some Swiss Francs from Travelex. When the lady behind the counter asked me how I'd like to pay, I said through debit card. She then told me I would need photographic id, which was a pain, because I didn't have any on me. She then told me that if I wanted to pay in cash, then she wouldn't need ID.

So I didn't use my debit card in Travelex, and type in my PIN there (the UK now uses Chip and PIN rather than signatures to authenticate purchases). Instead, I walked 400m to an ATM, used the same Debit card and same PIN to take out £100, walked back to Travelex with the £100, and then used the cash to get some £100 worth of Swiss francs.

So the puzzle is this - given that I would have used the same card and same PIN in both situations, what possible reason was there for Travelex to be happy with doing this second method without ID, but not the first? Read on for my suspected answer, or think about it yourself for a minute...


I think there was no added security, just an exchange of risk. Consider if it had been a stolen card and PIN. If I had just used the card at Travelex they would have taken some liability. By forcing me to walk to the ATM, if the card had been stolen, the ATM would have taken some liability. In order to take this risk of liability, they require photographic ID to reduce their risk. So instead, they gave me the risk of walking through the streets of London with a lot of cash. As a result, the transaction was far more anonymous, and so more vulnerable to money laundering, and I was at more risk of being mugged, but neither of those hurts Travelex.

Of course, this is very sensible of them. The best solution is for me to carry photo ID.

Wednesday, March 22, 2006

Writing is like UI design

Writing documents is just another form of user interface design. Especially if those documents are examples or tutorials. That might be a bit of a geeky way of looking at the world but I think it is true.

I was reading this post from Jensen Harris on how difficult it is get users to criticise user interfaces. He calls it "Usability Stockholm Syndrome". Meanwhile, from his body language I could tell one of my co-workers was obviously not that happy with a document I had written on recovering if one of our systems has an error. However, I found it really hard to get him to tell me what could be improved about it. He kept saying "No it's fine." Or "It's adequate." I had to really emphasise I want to improve both my document and my writing abilities to get some useful feedback.

This reminded me of reading a great book on writing software manuals - the User Manual Manual by Michael Bremer, who also wrote Untechnical Writing. In it he looks a trying to document a user interface. Unfortunately accomplishing the simplest task requires paragraphs of difficult prose, operating 200 different GUI controls. He says it's often much better to fix the user interface so performing the task is easy, then writing the documentation will just be an easy to understand paragraph.

There are other similarities between writing and developing user interfaces:
  • The end users don't always know how to improve them, but they know when they find them difficult to read or use
  • Important elements have to come to hand quickly, more obscure details can be left until later or put somewhere more obscure
  • Eat your own dogfood is necessary for quality but not sufficient
  • Hallway usability tests work for both
There are probably a lot more, but these are the first few that come to mind. I'm not sure what benefit realising this similarity brings to the world, but when I look at articles about writing or user interface design in the future, I might try and transfer the ideas. After all, the best innovation comes from stealing ideas from other fields and applying them in a novel way.