Cryptosmith

Over the years, our family has bought three copies of the Crosby, Stills & Nash album. My wife and I each bought a vinyl copy back in the ’70s. Recently we bought a “clean” (not copy protected) copy from the iTunes music store. I expect that’s the last time anyone in our family will have to buy a copy of that album, including all our descendants.

I believe that music sharing is “fair use” within a family. I’m inclined to feel that way about video, and no doubt I’ll feel the same way about digitized books. Cousin Jon sent me a couple of links describing “do it yourself” book scanners. I need to get myself one of those. But a family library of digitized books has an interesting implication for publishers: it will decimate the reprint market. My (not-yet-existing) great grandson won’t ever have to purchase a copy of Pride and Prejudice and should never have to buy any other books I collect in digital form.

Continue Reading »

Posted under History of Technology & Tech Teaching | No Comments »

I’ve always been a fan of graphic presentations. More people understand graphs and diagrams than understand equations. While this is a bad thing in some ways, it remains a fact. So it’s always great to see a graphical representation of a really difficult set of concepts.

Jeff Moser Fisher has posted A Stick Figure Guide to the Advanced Encryption Standard (AES). He has wisely structured it in layers. Interested readers can learn about AES to their level of interest or understanding: they can get the history and process, the high-level summary, or go diving into S-boxes.

Great!

Posted under Security & Tech Teaching | No Comments »

I first learned about computer architecture back in the 1970s. Much of what I learned came from a set of  block diagrams for the old Whirlwind computer built at MIT.  A few years back I had the document scanned in.

Yes, it’s built out of vacuum tubes. But it is also the complete design of a stored program digital computer in about 200 pages.

Continue Reading »

Posted under History of Technology & Tech Teaching | No Comments »

A reader asked for more details on the RC4 and block cipher mode functions I wrote in Matlab.

To recap, I needed a ‘block cipher’ to produce a complete example of how a straight block cipher fails to hide large patterns in the output, and how an appropriate block cipher mode yields something akin to white noise.

Wikipedia has a “penguin” example with a block encrypted version (penguin still visible) and a block of white noise. The white noise represents what the block mode output is supposed to look like as opposed to being the genuine output of a block cipher mode. So I built this ‘real’ example, more or less.

I didn’t have a block cipher that worked with small blocks. But I knew it wasn’t hard to implement RC4. So I created a function to map 8 bytes of data into 8 bytes of ‘ciphertext’ to simulate the block cipher.

Continue Reading »

Posted under Security & Tech Teaching | No Comments »