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  • 0 posts edited
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  • 16 votes cast
Mar
27
comment Value of security through amiguity?
Is the revelation of a (one correct, though by itself meaningless according to you) sequence of the "plain text values" a critical issue of security? If yes, the adversary needs only to brute-force all 256 keys (the key space is quite tiny) IMHO.
Mar
26
comment autocorrelation and entropy of historical ciphers
Concerning entropy, cf. a thread initiated by me: crypto.stackexchange.com/questions/33231/entropy-calculation
Mar
23
revised Unicity-distance of Playfair
added 241 characters in body
Mar
23
comment I am trying to generate a permutation of polynomial with order m
I have an encryption software named PERMUTATIONPOLYNORMIALS which contains functions dealing with their generations on computer. See s13.zetaboards.com/Crypto/topic/7340875/1/
Mar
21
comment Unicity-distance of Playfair
Playfair works with pairs of characters. It seems to me to be strange that the unicity distance is not an even number. Do you happen to have a bit more information (than the single value on that web site) on how the actual computation process for Playfair was done?
Mar
18
comment Testing implementation of cryptography algorithms: Brainstorm
I vaguely remember that many years ago there was a news saying that the kernel of an OS was successfully verified by a program verification system but I unfortunately didn't take any note of the reference.
Mar
18
asked Unicity-distance of Playfair
Mar
17
comment Do these new insights into prime numbers affect encryption security?
The phenomenon is IMHO reminiscent of Benford's Law in another context.
Mar
16
comment Is there an asymmetric algorithm that can perform double encryption?
I wonder how you got the value 88. If the block size of the plaintext material is mb bits (mb even), It is practically easy to obtain an RSA modulus n (n > 2**mb) that has mb + 2 bits. See Example 2 in Appendix of s13.zetaboards.com/Crypto/topic/7234475/1/ This implies that the differences between the bit sizes of successive elements in the sequence of RSA moduli could be as small as 2.
Mar
15
comment Is there an asymmetric algorithm that can perform double encryption?
If you have a sequence of RSA moduli that are strictly increasing and you have plaintext materials seperated into blocks of a constant size that is smaller than the least modulus, you could evidently do that multiple RSA encryption in the ordering of the sequence of the moduli..
Mar
14
comment Difference between MAC and Authenticated Encryption?
A MAC is only an integrity check, it isn't authentication in the sense of proving that the sender is indeed the right person.
Mar
6
comment Why is not there any ideal S-Box?
I am a layman and hence not sure at all whether the following paper could eventually have some relevance in the present context or not: K. Nyberg, Perfect nonlinear S-boxes, EUROCRYPT'91, pp 378-386.
Mar
6
comment Why haven't we proven many things computationally secure yet?
Why do you think that the proof of the information security of an (ideal) OTP isn't satisfactory?
Mar
6
comment Secret key agreement by public discussion from common information
As layman, I can't argue withj you at all. But there seem to be indications of much work being done on the noise issue following that seminal paper and even attempts of patent applications.
Mar
5
asked Secret key agreement by public discussion from common information
Mar
3
comment Public-key encryption with associated data
[Addendum] Pardon, in the example the IV is from system randomness. But in your context h is from your own choice, if I don't err, so you can substitute h for IV in the example.
Mar
3
comment Public-key encryption with associated data
I use RSA to encrypt blocks of plaintext in the way of block cipher with PCBC block-chaining. There is an IV that is pseudo-randomly generated with a session key and there is also an integrity check. IMHO that IV meets your requirement of h. In case that's indeed true, please look at Example 3 in the Appendix of s13.zetaboards.com/Crypto/topic/7234475/1/ (Please kindly tell, should I have misunderstood your post.)
Mar
3
comment How to calculate entropy of output of a PRNG
I don't know but doubt the feasibility of proof of the kind indicated in mikeazo's comment. On the other hand it's remarkable in my view that e.g. AES in counter mode could with 128 or 256 random bits generate an extremely long bit sequence that is commonly considered to be highly secure in practice.
Mar
3
comment Entropy calculation
Certainly, but that only weakens the problem and doesn't basically eliminate the problem in my view. Another issue is how to judge whether an entropy value computed is sufficiently good. I mean for statistical tests one has confidence intervals so that one knows what the values obtained signify. Entropy values seem to be fuzzy in comparison.
Mar
3
comment Entropy calculation
You have pointed to the fact that the entropy value computed is the same for all permutations of a sequence. But therein is IMHO a basic problem with Shannon's formula. Suppose a fairly random looking alphabetical sequence A gets a correspondingly good entropy value u. Sort it to B such that all a's are at the front, followed by b's etc. Then B is evidently less random than A but has the same entropy value u as A.