Ethan Heilman
Reputation
1,390
Top tag
Next privilege 2,000 Rep.
 Apr 15 comment Non-iterative cryptographic hash functions It has, thanks for your help. Apr 14 comment Non-iterative cryptographic hash functions I agree that non-iterative is a bad word to use for this property. What do you think about non-streaming compression? I really like where you are going with this however I'm concerned about the following situation: Let $G(x) = md5(x)||x$ and $H(x)=md5(x)$, wouldn't this allow me to define $md5(x)$ as "non-iterative/non-compressing"? Apr 13 comment Non-iterative cryptographic hash functions @ChrisPeikert SPRPs exist for any length, thus for each $|m|$ we choose a SPRP with the correct domain size. Apr 10 comment Non-iterative cryptographic hash functions @otus Consider two messages $m$ and $m'$ where $f(m_2||m_3||m_4||m_4||m_3||m_2) = f(m'_2||m'_3||m'_4||m'_4||m'_3||m'_2)$ and $m_1 = m'_1$. You don't actually need to know what $m_1$ is to know you have a collision. Part of the reason I asked this question was that I was looking for a better formal definition of non-iterative because I am not satisfied by the definition I currently have. Apr 10 comment Non-iterative cryptographic hash functions @otus yesterday If $h$ is an iterative hash and $|m|$ is significantly longer than the message block size then you can compress most of the messaged into $f(m||r(m)\mid_b)$ and compress the remainder in a second call to $f$. One test if something is an iterative hash is: 'can I cause a collision prior to reading the entire message?' Apr 9 comment Non-iterative cryptographic hash functions I did some of the differential resistance work on MD6 so I'm a big fan of the design. Its a nice property of a non-iterative hash functions that you can tree hash them into an iterative design if you want to. Apr 8 awarded Promoter Apr 5 reviewed Approve Non-iterative cryptographic hash functions Apr 3 revised Non-iterative cryptographic hash functions added 75 characters in body; edited title Apr 3 comment Non-iterative cryptographic hash functions @pg1989 Sponge-based hash functions like Keccak are considered iterative since the potential message space is much larger than the intermediate state (the sponge). One could imagine a construction in which the intermediate state grew in space to ensure no message entropy was lost, but it wouldn't be a sponge construction. Apr 3 comment Non-iterative cryptographic hash functions @pg1989 Added a more precise definition. Apr 3 revised Non-iterative cryptographic hash functions added formal definition Apr 3 revised Non-iterative cryptographic hash functions added 2 characters in body Apr 3 asked Non-iterative cryptographic hash functions Mar 11 awarded Nice Answer Feb 1 awarded Good Question Jan 29 awarded Nice Answer Dec 23 accepted Would the ability to efficiently find Discrete Logs have any impact on the security of RSA? Aug 27 awarded Famous Question Jul 12 awarded Yearling