Nik Bougalis
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 Jun 23 awarded Constituent Apr 11 revised Is there a simple zero knowledge proof of $x$ for $b=x^x\pmod p$? Math formatting Apr 11 suggested approved edit on Is there a simple zero knowledge proof of $x$ for $b=x^x\pmod p$? Sep 9 awarded Critic Apr 10 awarded Autobiographer Mar 25 comment Where can I begin to study the math behind modern cryptography? I don't know that your book recommendation is as good as you make it out to be. Personally, I think that "Applied Cryptography: Protocols, Algorithms, and Source Code in C" by Bruce Schneier and "Cryptography Engineering: Design Principles and Practical Applications" by Ferguson, Schneier and Kohno are both superior books in every sense of the word. Mar 25 comment Where can I begin to study the math behind modern cryptography? While it's certainly true that the larger Universities will have courses in cryptography, they may not be good courses. The fact is that few Universities have really good cryptography courses that will provide a solid foundation. Most don't have any at all, and they just skim over the subject. At my University, I personally found that the courses offered by the Mathematics department (particularly, courses in discrete math, Galois theory, etc) were much more in-depth and useful in theory and practice than the course offered by the Computer Science Department. Mar 22 comment What is the difference between a hash and a permutation? Right - I agree with both your points: it's not a hash function in the cryptographic sense, and cryptographic hash functions aren't just be mere permutations of the input. Mar 22 awarded Commentator Mar 22 comment What is the difference between a hash and a permutation? Your analysis is certainly extensive and detailed, but I must object to the statement that a "hash cannot be a permutation". Generally speaking you are correct, but given appropriate constraints a hash can be a permutation. Consider, for example, a hash function H(x) that one-to-one maps from every possible 16-bit integer to some other 16-bit integer by reversing the bits of the input (or, alternatively, XORs the incoming integer with the 16-bit value 0x029A). Mar 22 comment What is the difference between a hash and a permutation? @rath - Thanks, but that's alright. I think that my comment nicely supplements Oleksi's existing answer and works better in this context than as a standalone answer. Mar 22 comment What is the difference between a hash and a permutation? Right, a permutation will permute it's input and give you back something that is exactly the same length and has exactly the same elements as the input - just jumbled up. A hash function is a compression function - it takes something of arbitrary length and squeezes it down (or stretches it up) to a fixed length. Nothing stops you from treating a permutation as a hash function if you want to map fixed sized inputs to the same size output, but a permutation and a hash are different things. Mar 20 comment Google is using RC4, but isn't RC4 considered unsafe? @WatsonLadd I think it's somewhat unfair to attack an answer that, at this point, is 2 years old and make it appear as if it was "completely and utterly wrong" to begin with - especially when it isn't! Yes, new evidence has come to light about the security of RC4 when used with TLS/SSL and a comment noting that (very important) fact should be made. Yes, the answer could, possibly, be updated to account for the new information. Dec 21 revised Why is it important that phi(n) is kept a secret, in RSA? Mention that P and Q must be kept secret. Dec 21 comment Why is it important that phi(n) is kept a secret, in RSA? That's a fair point; I could have added a note about that, but the fact is that $P$ and $Q$ should be kept secret is well known and the original question was: "Why is it important that $ϕ(n)$ is kept a secret, in RSA?" Dec 20 awarded Teacher Dec 20 awarded Editor Dec 20 revised Why is it important that phi(n) is kept a secret, in RSA? deleted 8 characters in body Dec 20 comment Why is it important that phi(n) is kept a secret, in RSA? Beat me to it... perfect explanation. Dec 20 answered Why is it important that phi(n) is kept a secret, in RSA?