Thin Air

STS 2004: Cryptography and Smalltalk

Martin Kobetic made a really excellent presentation on VisualWorks Cryptography API. He walked through the major elements of cryptography - stream cyphers, block cyphers, message authentication codes, hashes, digital signatures etc. In each case he demonstrated the VW implementation.

The surprising thing that became apparent as Martin spoke is just how simple this stuff actually is. The VW API is extremely simple; generally you can do straightforward tasks with a couple message sends. Even the implementation seems pretty straightforward - the hard part isn't making it work, but making sure there are no hidden vulnerabilities..

One aspect of the presentation was very, very cool. The slides were presented using a custom VW app which had a very effective method of demonstrating the various cyphers. By selecting an area of the display, Martin could apply a cypher to that part of the display bitmap. This was really handy for visualizing encryption - after applying the cypher, blocks of the screen would appear to be white noise. He also did a great demonstration of the catastrophic effect of reusing a key with a block cypher - when two areas of the screen were encrypted with the same key and overlaid, the original images were plainly visible, no decryption necessary.

Congrats to Martin for a very clear presentation of a difficult topic.

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