Cryptosmith

John Fremlin has implemented a dynamic web server in Lisp. He claims that it beats the socks off of everything else. If we’re comparing Lisp against PHP, Python, Ruby, and similar scripting languages, I wouldn’t be surprised if he proves to be right.

Lisp is almost the closest-to-the-machine text language interpreter there is. Forth might beat it for closest, but Lisp is soo much more powerful. Moreover, it’s possible to build sane programs in Lisp that you can actually analyze. That gives us a slight hope of building reliable and secure web servers as opposed to the cobbled together things we have to live with.

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Critics and comics sometimes say that government insiders get more accurate information from CNN than from the CIA. Now we have ‘open source spying’ (Wall Street Journal). There’s a grad student who, via his “North Korea Uncovered” web site, is documenting all sorts of details of that notoriously secretive country. Thanks to Google Earth, he is constructing an annotated map of the country, highlighting prisons, nuclear activities, palaces, and so on.

While I don’t believe this sort of thing can, by itself, eliminate the CIA, but I really believe we could cut our spying costs and improve the results by opening up the analytical process. There’s a claim that our cheapo F-16s did better than the more costly fighters during Iraq I – there may be lots of ways improving defense while spending several billion less.

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A while back I used graphical images to illustrate why you never, ever want to reuse the keystream of a stream cipher. Recently I’ve constructed similar examples to show the role of modes in using block ciphers. There’s a nice set of block mode examples in Wikipedia, but I wanted to include the real result of applying the mode.

While cryptographic neophytes may want to know why the second encryption clearly failed (if you can read the message, the encryption failed), cryptographic experts may find it interesting to see other examples of cryptographic failures appearing graphically.

[There is a later post with more info on RC4 in Matlab]

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Posted under Security & Tech Teaching | 2 Comments »

The easiest way to share files on a desktop computer is for everyone to use the same login, and leave all the files on the desktop or in the “Documents” folder.

On the other hand, a desktop can be a personal thing. If I put a file somewhere, I like to know it’ll still be in that spot when I get back. Computers are tricky enough. We don’t have to add the work of other unpredictable humans to make them hard to use.

Once a household starts using multiple logins, you run into a completely different problem: how do you share things? I took all those pictures and my daughter wants to see them. We took turns typing in Xmas presents as we opened them, now where do we put the list so everyone knows what Thank You notes to write?

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