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  • 0 posts edited
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  • 16 votes cast
Feb
27
comment Applicability of birthday attack to AES brute force
Does your 2nd paragraph claim that "we need to search half of the key space to find a given key with odds 50%"? If yes, I have a problem with my logic: Following the birthday problem, keep generating randomly keys, test them for correctness and independent of result put them into a room, until the number of keys there achieves the collision estimate. Now consider the right key enters that room. Isn't it that with a 50% chance it will find that there is an already existing copy of it? If so, what 's wrong with the other argument of needing trying keys of a number of half of the key space?
Feb
26
comment What is a branch number in the PAEQ algorithm?
@asukaev: A paper in which branch number is involved is: www.mathnet.or.kr/mathnet/kms_tex/982865.pdf
Feb
26
revised Practicality of codebook in current-day secret communications
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Feb
26
revised Practicality of codebook in current-day secret communications
added 148 characters in body
Feb
25
revised Practicality of codebook in current-day secret communications
added 241 characters in body
Feb
25
comment Historical algorithm which is frequency analysis resilient
A recent nice paper on the VIC cipher available on the Internet is: tandfonline.com/doi/full/10.1080/01611194.2015.1028679
Feb
25
comment Historical algorithm which is frequency analysis resilient
You are right but I thought you were considering only "classical" schemes. An ideal OTP would lead to perfect security in the sense of Shannon (though it needs some nice work in practice).
Feb
25
comment Practicality of codebook in current-day secret communications
Many thanks for the comment. BTW I was elsewhere reminded of the use of codebooks in WWII, in particular the interesting history of code breaking in en.wikipedia.org/wiki/Battle_of_Midway
Feb
25
revised Practicality of codebook in current-day secret communications
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Feb
24
revised Practicality of codebook in current-day secret communications
added 122 characters in body
Feb
24
comment Practicality of codebook in current-day secret communications
@fkraiem: Indeed I don't see the correctness of your argument. The strength of a codebook certainly depends on its design and session use, in ways similar to encryption algorithms.
Feb
24
comment Practicality of codebook in current-day secret communications
@fkraiem: Do you have to securely protect your encryption keys? Anyway, sending an encrypted message over the Internet is an act whose existence is readily and simply available to any current law enforcement authority worthy of its name.
Feb
24
comment Practicality of codebook in current-day secret communications
@fkraiem: Which "strong algorithms"? Do you mean encryption algorithms? If yes, see my last comment (i.e. one has the advantage of avoiding to have matters to do with law enforcement authorities which attempt to intrude into people's privacy as one amply sees in the recent news).
Feb
24
comment Historical algorithm which is frequency analysis resilient
IMHO without homophones, i.e.the alphabet sizes of plaintext and ciphertext are the same and the length of the texts are identical, it is not feasible to change the probability distribution (in reality), except in cases where some characters happen to be absent in the particular plaintext given.
Feb
24
comment Practicality of codebook in current-day secret communications
With the arguments of my OP, top secrect communication isn't necessarily a hard problem, or is it? (And all the discussions like enforcing delivery of encryption keys or implanating "official" backdoors would appear to be more or less "Much Ado about Nothing".)
Feb
24
comment Practicality of codebook in current-day secret communications
@fkraiem: I doubt to have properly interpreted what you wrote. I mean my OP concerns the security of the message (i.e. independent of the hardware involved).
Feb
24
asked Practicality of codebook in current-day secret communications
Feb
23
comment Doubling the block length of a given block cipher
The scheme could apparently be useful if a current secure block cipher at a future timepoint becomes insufficiently secure due to growth of adversary's computing power (including the case when the dream of quantum computing comes true), since it could obviate the necessity (or at least urgent necessity) of a new design of block cipher in response.
Feb
22
comment Secure entropy extractor for thermal noise collected from camera input?
@Rex: IMHO nothing 100% perfect could be obtained in this world (excepting in pure math). If one iteratively does "xor-ing of two sequences followed by von Neumann unbiasing" a sufficiently large number of times, wouldn't the result tend to approach the practically unachievable ideal perfection?
Feb
21
comment Doubling the block length of a given block cipher
Erratum: In place of "subblock[j+1 mod m]" please read "subblock[(j mod m) +1]". Sorry.