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Cryptography

Launched Q&A site for software developers, mathematicians and others interested in cryptography.

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3  
Possible duplicate: SO, math.stackexchange.com or area51.stackexchange.com/proposals/8766/…. @Mark Robinson, do you agree? – Maniero Nov 15 '10 at 23:08
3  
@bigown - I'm not an expert so my honest answer is: I don't know. But since the answer to my question above is that it is for people doing cryptography, and since it already has 57 followers, I think it stands in its own right. – Wikis Nov 16 '10 at 8:20
9  
@Ravi, @Mark, Since this site was not mergeed with the security.stackexchange.com one, and that one does cover applied cryptography, as in developers using encryption and building cryptosystems, I would say this should be more in the direction of research / theoretical / conceptual / algorithmical / mathy parts of crypto. – AviD Nov 19 '10 at 9:55
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15
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4
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Scope of Cryptography proposal overlaps with other existing sites

jul 13 '11 at 0:24 Community♦ 1

discuss this proposal

61 Example Questions (9 closed)

active newest votes
up vote 22 down vote
How can I generate large primes for public key cryptography?
added by Wikis Jul 31 '10 at 16:34
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up vote 20 down vote
What's the purpose of the S-Boxes in AES?
added by Eclipse Jul 30 '10 at 20:06
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up vote 20 down vote
Besides the obvious O(√N) speed-up, does a Quantum Computer have any advantages in breaking AES?
added by KennyTM Aug 3 '10 at 10:43
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I'd peg this for off-topic until/unless working quantum computers exist (outside the slashdot news stories about theoretical work towards them, I don't know of any that work) – warren Aug 3 '10 at 14:30
1  
I agree with the off-topic designation but general quantom computer + crypto questions (theoretical) should be allowed, I think. – Shul Aug 3 '10 at 20:41
4  
If you are encrypting something today, you don't only want it to be secure against attacks that exist today. You might also want to prevent an attacker from decrypting tomorrow, next year, or in a decade. Perhaps even longer. So this is on-topic. – Zooko Aug 4 '10 at 21:03
2  
Post-quantum crypto is an active research area, and it seems odd to simply ignore it because current QC implementations are on too small a scale to pose a threat to RSA or El Gamal. – Joe Fitzsimons Sep 17 '10 at 15:27
up vote 18 down vote
How does symmetric key encryption differ from asymmetric key encryption?
added by Ravi Vyas Jul 30 '10 at 5:45
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8  
Imho that's way too basic for "people doing cryptography". – Tadeusz A. Kadłubowski Aug 1 '10 at 18:13
1  
True, if you think of it in a higher level , but what about the match of both the systems? may e we should add that :) – Ravi Vyas Aug 1 '10 at 19:34
2  
Imo it's appropriate, since knowing when to use which is just as important. – wez Aug 3 '10 at 11:04
Sorry for the typo , its math and not match and "may be" and not "may e" :-) – Ravi Vyas Aug 4 '10 at 16:25
up vote 18 down vote
What is an initialization vector?
added by Blorgbeard Jul 30 '10 at 8:04
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3  
I think the target audience should know what an initialization vector is. – Frédéric Grosshans Nov 16 '10 at 15:58
@Frédéric: I still think it would be good to cover some basic questions. It might also attract comments alluding to interesting special cases that most people have not heard about. – Thilo Dec 3 '10 at 2:44
up vote 17 down vote
Why does RSA require longer keys when compared to a symmetric key algorithm?
added by Ravi Vyas, edited by WikiSpeedia hang-around Aug 2 '10 at 13:27
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up vote 11 down vote
What are the practical difference between 256-bit, 192-bit, and 128-bit AES encryption?
added by samoz Aug 2 '10 at 18:50
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up vote 9 down vote
Why is Triple-DES acceptable, while normal DES is not?
added by samoz Aug 2 '10 at 18:50
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2  
Why was this voted as not a good example? – samoz Aug 10 '10 at 2:35
up vote 9 down vote
I'm writing a program for hard drive encryption. What cipher modes are a good choice for this application?
added by Jack Lloyd Aug 4 '10 at 18:47
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Good question :) – Ravi Vyas Aug 12 '10 at 19:32
up vote 8 down vote
What best practices should I follow when using a salt during encryption?
added by wez Aug 3 '10 at 10:56
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up vote 7 down vote
How do I map a random point on an elliptical curve (with at least m bits of min-entropy) to an m-bit integer in an unbiased way?
added by PulpSpy Oct 16 '10 at 21:36
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up vote 6 down vote
How do I break [x] encryption?
added by user452 Jul 30 '10 at 15:42
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2  
Too vague? Although, an index of modern cryptanalytic techniques would be a great thing to have. – Zack Aug 4 '10 at 21:11
up vote 6 down vote
In TLS client and server negotiating a secret which is used to create session keys. Why does this secret need to be negotiated?
added by qbi Jul 31 '10 at 19:43
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1  
This is good because it gets at protocol design, which is often the weak point in a cryptosystem. It might, however, be too specific to be interesting. – Zack Aug 4 '10 at 21:14
up vote 6 down vote
In what countries is the usage of cryptography allowed/forbidden? [closed]
added by qbi Jul 31 '10 at 19:45
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closed as off topic by Jack Lloyd, Ravi Vyas, igelkott, snmcdonald, Brad Mace Oct 17 '10 at 2:59

This question does not relate to the topic of the proposal.
It was closed as part of an automated migration of off-topic to close votes on September 29, 2011.

I would've thought that's a good question for security.stackexchange.com as it's about risk management and policy, and not necessarily a question for crypto mathematicians. – Graham Lee Dec 15 '10 at 13:34
up vote 5 down vote
How can I defend against timing attacks?
added by qbi Jul 31 '10 at 19:39
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up vote 5 down vote
How can I compute large primes?
added by bitmask Oct 16 '10 at 18:14
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up vote 4 down vote
How was the "Enigma" machine broken?
added by Ravi Vyas, edited by WikiSpeedia hang-around Aug 2 '10 at 13:27
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3  
Well documented elsewhere. Unlikely to gain new insights. – igelkott Oct 2 '10 at 23:17
up vote 4 down vote
Is there a way to combine two or more hashes such that if any one of them is collision resistant the overall construction is also collision resistant?
added by Jack Lloyd Aug 4 '10 at 18:50
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up vote 3 down vote
What's the difference between encryption and a hash?
added by user452 Jul 30 '10 at 15:41
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6  
I consider this not a good example, because the targeted audience should know in detail what the difference is. – qbi Jul 31 '10 at 19:23
up vote 3 down vote
Can I use a symmetric cipher as a hash function? How should I properly use it?
added by qbi Jul 31 '10 at 19:34
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up vote 3 down vote
What should be minimum RAM requirement to implement TLS_RSA_WITH_AES_128_CBC_SHA? (I am asking about number of bytes not KB) on 32-bit RISC processor.
added by ralu, edited by WikiSpeedia hang-around Aug 7 '10 at 14:46
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2  
Great question. Would be even better with the name of the hardware architecture. – Tadeusz A. Kadłubowski Aug 1 '10 at 18:16
up vote 3 down vote
How crucial is the use of random oracles in the Fiat-Shamir heuristic?
added by Mikero Aug 20 '10 at 0:30
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up vote 3 down vote
Why are S and P boxes utilized in symmetric algorithms?
added by warren Aug 31 '10 at 13:45
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up vote 3 down vote
In "certificateless public key cryptography" schemes (Al-Riyami and Patterson 2003, Liu et al 2007, etc) do "partial private keys" need to be secret?
added by Zack Sep 20 '10 at 23:24
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up vote 3 down vote
Is there is a secret sharing scheme which is both additive and multiplicative ?
added by M. Alaggan Nov 10 '10 at 20:36
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up vote 2 down vote
What are prime numbers used for in cryptography?
added by googletorp, edited by Wikis Jul 31 '10 at 16:33
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May be we should state prime numbers (instead of big prime numbers) – Ravi Vyas Jul 30 '10 at 7:16
1  
I voted not a good example because "What's the difference between encryption and a hash" was assumed to be known by target audience, this question would fall under that definition as well. – samoz Aug 10 '10 at 2:34
@samoz - but if you're new to the field, or just "interested", you may not know about asymmetry yet – warren Aug 10 '10 at 2:44
I also voted not a good example because I've seen this question asked and answered in math.so. Some overlapping is just fine, but we might as well point to that resource. An explanation it is also found easily in Wikipedia. Maybe adding to the question some details that are not clear would be better. – skd Dec 10 '10 at 12:51
up vote 2 down vote
How can I generate cryptographically strong random values on [operating system/crypto library]?
added by Eclipse Jul 30 '10 at 20:08
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seems more like a stackoverflow question to me – Zack Aug 4 '10 at 21:12
If just based on theory or general methods , I think this is on topic – Ravi Vyas Aug 5 '10 at 3:52
up vote 2 down vote
Under what assumptions is PBKDF2 a pseudo-random function? Do I need to assume the hash is a random oracle? Do any of the HMAC/NMAC proofs apply?
added by Jack Lloyd Aug 4 '10 at 18:53
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up vote 2 down vote
Which algebraic groups currently have efficient/practical implementations of bilinear pairings?
added by Mikero Aug 20 '10 at 0:26
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up vote 2 down vote
How are S and P boxes chosen?
added by warren Aug 31 '10 at 13:45
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up vote 2 down vote
The Skipjack block cipher uses an 8 bit sbox (called F in the spec). Does this permutation have an underlying mathematical structure, or is it random?
added by Jack Lloyd Sep 8 '10 at 19:32
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up vote 2 down vote
Is there an implementation of Gentry's fully homomorphic encryption scheme? How efficient is it?
added by PulpSpy Oct 16 '10 at 21:28
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up vote 2 down vote
Can I use a hash function as random extractor? What about a block cipher?
added by PulpSpy Oct 16 '10 at 21:33
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up vote 2 down vote
Can the Dodis-Yampolskiy verifiable random function accept full-sized inputs? Is there an efficient alternative?
added by PulpSpy Oct 16 '10 at 21:34
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up vote 1 down vote
How do the bitslice sboxes used in the Noekeon and Serpent block ciphers work?
added by Jack Lloyd Aug 4 '10 at 18:54
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up vote 1 down vote
What is the difference between IND-CPA security and IND-CCA security guarantees ?
added by M. Alaggan Nov 10 '10 at 20:34
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up vote 1 down vote
Are there cryptanalysis consequences to using a non-random salt during hashing?
added by AviD Nov 19 '10 at 10:00
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up vote 1 down vote
What's the difference between private and public key encryption?
added by Gordon Gustafson Dec 4 '10 at 0:54
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up vote 1 down vote
I'm considering making an in-the-web-browser digital signature add-on for e-laws / e-democracy. Any previous work in this area I should know about?
added by Dogweather Dec 7 '10 at 0:06
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up vote 1 down vote
What are the weaknesses of the cryptosystem X?
added by skd Dec 10 '10 at 12:55
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