Cryptography Stack Exchange is a question and answer site for software developers, mathematicians and others interested in cryptography. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

I have heard about ciphers that have a block length of 256 megabytes... That is huge. How well are they understood by the encryption community? I'm referring to PMC Ciphers.

Has anyone used such a cipher in a real world application?

share|improve this question
It's easy to construct a large block blockcipher from a normal block cipher with a factor 2 performance hit. So I see little reason to use dedicated large block blockciphers. – CodesInChaos May 30 '13 at 11:01
The website you linked is certainly full of bullshit. A 256 bit block and 256 bit key is certainly enough for almost everything. – CodesInChaos May 30 '13 at 11:02
This website sure looks dodgy. They push large blocks as an advantage without ever giving a reason. They declare that being able to use low-end devices is a downside (it's a downside for password hashing, which isn't what ciphers are for). They demonstrate the insecurity of ECB mode and claim that the underlying cipher is the problem. Their papers aren't peer-reviewed and somehow they claim it as an advantage. All in all, that's a load of snake oil. – Gilles May 30 '13 at 12:25
in that image comparison (encrypting a 6 bit grayscale with large patches of same color) is very skewed against AES by using ECB, the PDF only mentions CBC as an afterthought – ratchet freak May 30 '13 at 12:56
Apparently encryption primitives derived from PRP's must use padding as they have a fixed block size (??). Stopped reading there. Snake oil and the author is clueless. – Thomas Jun 8 '13 at 10:11

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Browse other questions tagged or ask your own question.