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Feb
25
comment RSA Key composition
@fgrieu: I was worrying that one might have different interpretations of "a number of n bits". A number with bits e.g. "1001" would be called by someone as a 4-bit number but it is less then 2**4. I just wanted to call to the fact that, in case one uses that interpretation, then a n-bit M could be less than 2 to the power n and processing a block having n bits could fail to work in the RSA equations.
Feb
24
comment RSA Key composition
It should be noted that, if an arbitrary message of size of n bits is to be processed by RSA, the modulus M must be chosen to be greater than 2**n.
Feb
11
comment Any efficient text-based steganographic schemes?
After quite some experiments in the said direction, I have found that for easy/conveinent work of the sender one has unfortunately to reduce the bit embedding rate to 1 bit per sentence. Description of the scheme and a code to verify by computer the correctness of the manual work is in: s13.zetaboards.com/Crypto/topic/7338098/1
Feb
3
comment Python implementation of a blind signature scheme which doesn't involve RSA
@user37203: What do you mean with "Generating good enough primes ....."? Together with your last post, do you mean that the prime number generation part of a big package is in practice fairly troublesome to check whether it's free of security problems (and impossible if the package is binary)? If so, I have had the same concern and implemented in some 50 lines of Python Maurer's algorithm (see HAC p.153) of generation of random provable (in contrast to highly probable) primes, available at s13.zetaboards.com/Crypto/topic/7234475/1
Dec
15
comment What would be the best plain text Cryptography method without the use of a computer?
Playfair tableaux have the advantage of being compact. You could also use a few of them to transcribe successive pairs or overlapping pairs.
Nov
5
comment What is the most computationally efficient way of generating pseudo-random permutations?
@user44353: You are right. (Anyway I don't know how.)
Nov
4
comment Multi-round Transposition/Playfair as a secure hand cipher in the computer age
If I don't gravely err, computers could be sufficiently secured, if only one takes correspondingly sufficiently efficient countermeasures. Computer encryption codes based on classical crypto have however advantage in the special case where one communication partner for some reasons is deprived of the possiblity of using computers. (BTW, I have a code employing multiple Playfairs available at s13.zetaboards.com/Crypto/topic/7215879/1 which you may like to compare with your scheme.)
Nov
4
comment Brute Force AES Calculations
There are quite a number of different AES implementations, some in high-level PLs, some in assemblers, and these may have fairly different efficiencies, even dependent on different hardware and OS environments. (BTW I have a passable C code for AES at mokkong-shen.privat.t-online.de which you may like to compare in efficiency with other implementations.)
Oct
19
comment Does the transposition cipher have a network application?
You have a typo: Not "transition cipher" but "transposition cipher". Perhaps it's advantageous for you to read something in a book, e.g. A. J. Menezes et al., HAC (available online), Sec. 7.3. Note that even modern block ciphers are principally based on transpositions and substitutions.
Oct
16
comment How do you test randomness?
Maurer's universal statistical test (see A. J. Menezes et al., Handbook of Applied Cryptography, sec.5.4.5 (available online)) may be of some interest to you.
Jun
25
comment Is it a good idea to use Lagrange/Newtonian interpolation for encryption?
Your description (and purpose of the scheme) isn't clear, I am afraid. Could you give a tiny concrete illustrative example with its usage in practice?
Jun
21
comment How can I find the multiplicative inverse in the first transformation of the SubBytes() transformation in AES?
If a computation is done in a finite field, there is IMHO barely a possibility to appropriately re-formulate that in terms of common arithmetic operations (for the purpose of rendering it easier to comprehend). You would have to either learn the basics of finite fields or take the results of others for granted, I am afriad.
Apr
2
comment Is substitution with random prefix codes secure?
@rath: I have deleted (2) corresponding to your suggestion.
Mar
30
comment Is substitution with random prefix codes secure?
I have duly correspondingly formulated my new question with the best care I could manage to do to limit its scope to the least minimum and posted it under the title "Any good means to enhance the security of encryption processing with random prefix codes".
Mar
29
comment Is substitution with random prefix codes secure?
I understand you mean that one should limit the scope of a question to the least minimum possible. So I'll have to ask a new question in the present context. Thank you very much for the guidance.
Mar
28
comment Is substitution with random prefix codes secure?
But IMHO in crypto one rarely uses one single algorithm (in the narrow sense) but a combination of confusion and diffusion in the terms of Shannon. So if one appropriately combine prefix-coding with e.g. certain transpositions, would that be a good defense against known/chosen text attacks? (In fact I have attempted to do such a combination in a humble scheme of mine recently (s13.zetaboards.com/Crypto/topic/7164646/1). Actually, it was because I was not very sure whether prefix-coding is "self-sufficient" that I did the original posting in order to learn more about its real strength.)
Mar
28
comment Is substitution with random prefix codes secure?
@figlesquidge: Done. Thank you.
Mar
28
comment Is substitution with random prefix codes secure?
Oh, I should have replaced "claim" with "claim according to my interpretation", since I am not 100% sure of the correctness of my interpretation (as I said, my understanding of the article is only partial). If the real claim is not correct, then the other phrase of mine would make sense IMHO.
Mar
26
comment Encryption of numeric value using playfair
If the matrix doesn't have 5, then you simply cannot process that character with that matrix. Perhaps you were expected to think of the use of a larger matrix than the one shown in the lessons.
Mar
14
comment How to best mix two arbitrary/random n-bit words?
The specific application that interests me currently would certainly be deemed too mundane from a theoretical point of view. In a certain encryption processing I am considering there are two n-bit words, x and y, one on the plaintext side and one on the ciphertext side (but neither is directly plaintext or ciphertext). I like to combine them into z and sum the z's of all preceding blocks into a value s and use that to chain the blocks. It's my thinking that, if z is "somehow" optimal in capturing the randomness of x any y, then the chaining would also be fine. Would that satisfy your query?