Need info on RC5 decryption

[Macavity]

9,225,283,403,065,065,472 keys in 1331 days, which they cited as being 1/2 of the total possible at... 210 Gkeys/sec .... rules out brute force.

There is a thread about e-books in the forums here that lists a ton of computer/crypto ones in 1 shot.. I remember it having a URL involving engineering and a .uk address as well. I do remember it having a ton of RC5 stuff in it, and explanations of how to solve based on parts you may or may not know.

As for IV... try conversions of KU, RT, KURT, TURK, TU, RK, and then add and subtract each. I saw the picture that you're looking at, and no one has mentioned anything about those letters in the upper left.. which has me curious if they're actually there for a visual distraction to mislead, or so blatantly obvious that most analytical will think it'd be too easy if that were the answer. I will do a bit more research and post as/if I find something.

Qu|rk-

Thanks for the data, Qu|rk! I'll take a shufty for the thread you mentioned, and pass the info on to the guys I'm working with.

[Qu|rk]

9,225,283,403,065,065,472 keys in 1331 days, which they cited as being 1/2 of the total possible at... 210 Gkeys/sec .... rules out brute force.

There is a thread about e-books in the forums here that lists a ton of computer/crypto ones in 1 shot.. I remember it having a URL involving engineering and a .uk address as well. I do remember it having a ton of RC5 stuff in it, and explanations of how to solve based on parts you may or may not know.

As for IV... try conversions of KU, RT, KURT, TURK, TU, RK, and then add and subtract each. I saw the picture that you're looking at, and no one has mentioned anything about those letters in the upper left.. which has me curious if they're actually there for a visual distraction to mislead, or so blatantly obvious that most analytical will think it'd be too easy if that were the answer. I will do a bit more research and post as/if I find something.

Qu|rk-

[octalpus]

Now THIS is how to ask a question!!!

[Macavity]

As you've no doubt guessed from the title, I've been trying to find information on decrypting a dataset that's been encoded using an RC5 schema - specifically RC5-64/12/8.

The reason I'm looking for it is for part of an Alternate Reality Game I'm involved in, called Perplex City. Part of the game involves solving puzzle cards in order to get information on a crime that's been committed (one which may or may not be tied to other crimes that have occurred, including the the murder of Perplex City's top investigative journalist, Pietro Salk), and the group I'm working with on one of the more difficult ones - #251, The Thirteenth Labor - has run into a dead end.

Now, the prevailing theory is that the data on the card has been encrypted using RC5-64/12/8 - just about everyone's agreed on that point. There is some disagreement, though, as to what initialization vectors were used (some are suggesting the ones found in this section of RSA Security's website), what the key is (most are leaning towards the one used by distributed.net), and similar matters.

I figured a good place to ask for information would be here, since it seems likely that someone here would be familiar with RC5-64/12/8 and thus be able to give us some pointers on decrypting the data.

So, if anyone could give us some pointers in that regard, we'd really appreciate it.