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Challenge "World Record Challenge: Break 65 Bits of AES"

Challenge "World Record Challenge: Break 65 Bits of AES"  

  By: admin on May 7, 2010, 2:29 p.m.

The longest key that has ever been publicly cracked by exhaustive key search was 64 bits long. The purpose of this challenge is to improve this world record by one bit.
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 Last edited by: admin on Oct. 31, 2021, 2:54 a.m., edited 1 time in total.

Re: Challenge "World Record Challenge: Break 65 Bit of AES"  

  By: Veselovský on Aug. 9, 2011, 9:13 p.m.

Hi,

It is a little bit confusing.
Can you explain in more detail what is meant by:
"The first 65 bits (of a key) must be guessed."
and then
"Your task is to guess the first eight bytes of cleartext."

If I guessed 65 bits of the key correctly, then why should I guess eight bytes of cleartext???
I can use the key to decode the ciphertext without guessing, no?
What am I missing?

Re: Challenge "World Record Challenge: Break 65 Bit of AES"  

  By: DarkFibre on Aug. 9, 2011, 9:24 p.m.

You don't need to guess all 128 bits of the key, just the first 65 bits, which would still probably take years of computing power.

They give half the pt so you know your key is right, you give the other half of the pt to prove it to them, probably because it's easier to type in words than a key (I wish all solutions involved typing in words). If your key is 1 bit off the entire pt is scrambled.

I think they just mistranslated "solve" or "provide" or "decrypt" into the word "guess" somewhere along the way. That's how I read it anyway, but I didn't stress it as it seems out of my reach.

Re: Challenge "World Record Challenge: Break 65 Bit of AES"  

  By: realkus on Aug. 11, 2011, 12:07 a.m.

DarkFibre is right. You need to guess 65 bits of the key. The word "guess" in this case is appropriate, because you have to find the solution by trial and error. You have to make guesses until you find the correct key.

Realkus

Re: Challenge "World Record Challenge: Break 65 Bit of AES"  

  By: realkus on Aug. 11, 2011, 2:09 p.m.

When you "guess" a key, you get a cleartext belonging to it. This means, with every key guess you make you automatically also guess a cleartext. So, the word "guess" is also appropriate for the cleartext.

Realkus


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