Category Archives: Crypto

September 24, 2007, 9:00 am

Happy Birthday, William Friedman

Today is the birthday of William Friedman, one of the fathers of modern cryptology and an unsung American hero from World War II.

Before Friedman, cryptology could be described at best as a hodgepodge of tricks and unproven methods for securing information. Some tricks worked better than others. But there was no math in cryptology to quantify the strength (and exploit the weaknesses) of ciphers, really, until Friedman came along and brought the power of modern statistical techniques to bear on such problems as breaking rotor-machine ciphers. He almost single-handedly broke the Japanese PURPLE cipher, and in what’s surely one of the greatest problem-solving feats of all time, his team was able to complete reconstruct a PURPLE cipher machine using only plaintext and ciphertext samples — no technical diagrams were used.

He later suffered a major nervous breakdown, blamed mostly on his in…

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May 14, 2007, 12:18 pm

Perhaps my favorite final exam problem ever.

Check out problem 5 on the final exam I am giving today in my Cryptology topics class.


Thanks, XKCD.

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April 25, 2007, 9:11 pm

PlayStations as distributed computing nodes

This is cool:

Stanford University’s Folding@Home project, which puts personal computers to work studying the complicated process of protein folding, could soon get a big boost from an unlikely direction. Starting this month, owners of Sony’s PlayStation 3 video-game console will be able to take part in the research project when they’re not busy playing games.

Researchers have recruited about 200,000 desktop machines to participate in the project, which has implications for medical science. But the officials are bullish about PlayStations, according to Scientific American, because the gaming devices actually perform some simulations faster than most computers.

Here’s the whole Scientific American story. And there’s lots more distributed computing projects where that came from, such as Project RC5 which our Mac mini at home crunches on all day and night.

[via Wired Campus Blog]

October 19, 2006, 12:20 pm

Fall Break overview

Fall Break is upon us, as is fall itself with rainy, cool weather today. It’s a break, but a full one:

  • This is the first day in over six weeks that I have had substantive time to work on the dual-degree engineering program. The deadline for curriculum proposals is coming up shortly and the thing needs to get done. I think I’ll make it. Some tweaking needs to be done: since we offer Calculus III only once every two years, students who want to do engineering but who start the program in even-numbered years can’t take it until they are juniors, which puts them a year behind in the engineering program. I’ve got a workaround right now for that, but it’s not pretty. So I am lobbying my department and dean to have Calculus III offered every year, like a normal math department would do.
  • This semester has been kicking my rear since about day 3 and hasn’t stopped. I have 14 hours’ of…

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September 7, 2006, 11:30 am

New Mersenne prime “probably” found

The Great Internet Mersenne Prime Search (GIMPS) home page is reporting that the 44th Mersenne prime has "probably" been found — i.e., the number has been registered with the GIMPS server and is undergoing checking — as of September 4. Verification should be done in a week. The 43rd one (found in December 2005) was over 9 million digits long; no indication of how big this one is, if it’s indeed a prime.

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June 20, 2006, 1:17 pm tuesday #7

This week’s look into my bookmarks brings us to…

Powers of Ten (the video)

I think I remember seeing this when I was a kid. It’s a fascinating visualization of the differences between different powers of ten. The video starts with a viewpoint one meter above a family at a picnic, then zooms out to 10 meters, then to 100, then to 1000, then… all the way to 1025 meters, and then back to 1 meter and down to 10-15. See for yourself here at YouTube. (Hmm… I tried to embed the video directly but it screwed up the site. Is there something special I have to do to make it appear?)

I only wish they did one like this using powers of 2, for use in my cryptology teaching materials. I have the hardest time convincing students that a 32-bit key is not just twice as secure as a 16-bit key, but 216 times more secure.

June 9, 2006, 10:56 pm

Technology banning, antique style?

I’ve been bidding in some eBay auctions over the last couple of days, the first time I’d done so in several months. I thought I’d do a little searching, just for fun, for antique cryptographic devices like one of these. I came across an auction for a 1945 NEMA Model 45 Enigma machine with a price of, er, $8939.99. Too rich for my blood, but could be fun to look at anyway. But when I tried to view the item, I got this (click to enlarge):

There’s another auction for a similar Enigma-like machine that gives me the same “somebody thinks you shouldn’t be viewing this” message.

So let me get this straight: I can’t view an auction of a 60-year old Swiss cipher machine, in the USA, because of legal restrictions? Are they the same legal restrictions that classified the posting of PGP to a web server as a violation of an arms control treaty? If so, maybe I should become an arms trafficker.

Or …

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June 7, 2006, 7:20 am “Tuesday” #5

As promised, here’s this week’s installment of Tuesday (a day late), where I pull a link from my bookmarks and highlight it. And as expected, it’s crypto-related this week: (read it as two words: enigma | is a very cool flash-based simulator for a three-rotor Enigma machine like the ones used by the German armed forces in WWII. I’ve used electronic Enigma simulators before for teaching purposes, both online and in prepackaged software, but this one by far has the best functionality and look-and-feel. The look somehow reminds me of something off the cover of a Neal Stephenson novel, which maybe was the intention.

You can set the rotors and the plugboard settings and then type a message in to get the ciphertext. As you type, it displays how the signal is routed through the rotors and plugboard to give the ciphertext letter. It works…

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May 26, 2006, 9:57 am

A game for your weekend pleasure

I’m preparing the mini-course I’m giving on the 8th, and I am doing a brief spiel on ROT13. This is a very easy (= weak) encryption technique implemented by shifting each letter in the plaintext forward by 13 places in the alphabet, wrapping around the beginning of the alphabet if necessary. For example, if the plaintext message is “MONDAY”, then the ROT13-encrypted version is “ZBAQNL”.

I’ve got a handy-dandy dashboard widget to do ROT13, and as an example I typed in “to be or not to be“, which encrypts to “gb or be abg gb or“. The interesting thing to notice is that the word “be” encrypts to “or“, and of course vice versa. Did Shakespeare know that would happen — as if to suggest that “be” and “or” are in some sense opposites?

So my challenge to you is: Find English words which, when encrypted with ROT13, become some other English word. There are some examples at the Wikipedia…

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May 7, 2006, 1:37 pm

And speaking of things geeky…

…Bruce Schneier brings us a link to rapper MC Plus+ (M C plus plus… get it?), who has done a rap about cryptography called Alice and Bob. Here’s a sample (so to speak):

DES is wrong if you listen to NIST
Double DES ain’t no better man, that got Dis’ed
Twofish for AES, that was Schneier’s wish
Like a shot from the key
Rijndael made the swish
But Blowfish is still the fastest in the land
And Bruce used the same to ECB and I’ll crack your ciphertext
Try CFB mode to keep everyone perplexed

Also includes a sample from Bablyon 5 to round out the geekiness. Make sure you read the comments too, which includes an appearance from MC Plus+’s beatmaker (“Mad love to all the real CS gangstas,” he says).

[tags]Crypto, DES, AES, Twofish, Blowfish, Rijndael, Geek, Bruce Schneier, MC Plus+[/tags]

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