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  • 0 posts edited
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  • 16 votes cast
Feb
20
revised Doubling the block length of a given block cipher
added 791 characters in body
Feb
20
comment Doubling the block length of a given block cipher
@Biv: I do mean what you wrote in your last paragraph. I don't understand why there wouldn't be a gain in security, since a double lengthed key is involved (that affects at least bruteforcing).
Feb
19
asked Doubling the block length of a given block cipher
Feb
19
comment Can RSA (theoretically) be used as a block cipher?
IMHO OP's main issue is to use RSA to encrypt data in bulk (s. his 1st paragraph), not to use a RSA-based block cipher to built another cipher in CTR or other modes of operations. I have done thus exactly what OP asked in Example 3 of my software s13.zetaboards.com/Crypto/topic/7234475/1
Feb
18
comment Is F5 still a viable steganography algorithm?
@waifsandmendicants: Perhaps you could also ask the authors of the paper you quoted. Failing that, you should IMHO at least look at the proceedings of conferences on information hiding in the LNCS published by Springer to try to find an answer to your question. (Note that papers on stego schemes not infrequently appear in journals on signal processing that belongs to electrical engineering.)
Feb
18
comment Is there any more asymetric-time permutation than x^3 (mod p)?
A thread "How to take integer cube root?" of yesterday in reddit.com/r/crypto/ seems to eventually have some relevance to your issue. (I have only taken a superficial look at it.)
Feb
18
comment Is there any more asymetric-time permutation than x^3 (mod p)?
Would the 5th power also work fairly well in this context?
Feb
18
comment Layman's explanation of encryption backdoors
@M'vy: To your "known example" I like to add the comparatively much more sophisticated scheme of that genre that was suggested by maartin many years ago (and recently elaborated by me on the Internet).
Feb
16
comment How to disguise ciphertext
@JohnHenckel: Don't the schemes mentioned in my previous comment well satisfy your requirements (especially as explained in your last edit), excepting the IMHO practically unavoidable disadvantage of fairly low stego bit rate? (I should certainly highly appreciate your evaluation of the schemes from the viewpoint of your concrete applications.)
Feb
16
comment How to disguise ciphertext
That is: you want to well hide the information (basically bits) of the given ciphertext in a covertext that is formulated in a natural language. I suppose it's understandable that the efficiency of such processing is naturally fairly low in general, i.e. the ratio of the length of the covertext to the length of the given ciphertext is fairly high. In case that inefficiency could be acceptable for your applications, you could try out two schemes of mine: s13.zetaboards.com/Crypto/topic/6939954/1 and s13.zetaboards.com/Crypto/topic/7338098/1
Feb
15
comment RSA : Double-Encryption and order of Encryption
@user3168961: I had a mistake (fortunately without consequence) in my writing which you certainly have noticed: 2**M-1 should read M-1.
Feb
13
comment RSA : Double-Encryption and order of Encryption
I suppose the context is encryption processing using keys of both the receiver and the sender, i.e. receiver's public key with modulus MR and sender's secret key with modulus MS. Since RSA processing with a modulus M results in numbers in [0, 2**M-1], the double processing is only sensible when the first processing uses a modulus that is the smaller one of MR and MS , for otherwise there could be truncations. (Whether this double processing is what one desires is another matter.)
Feb
4
revised Are there any practical methods of steganography?
added 674 characters in body
Feb
3
answered Are there any practical methods of steganography?
Jan
29
comment When we use permutation and random long sting to hide a message
But you could give a concrete trivial (may be no good for your intended purposes) example such that one clearly knows your underlying thought. Say, the English name is "Eve", the random string is ........(your choice), assuming that case is ignored.
Jan
29
comment When we use permutation and random long sting to hide a message
I may gravely err, but I surmise that your question might not be "well-formed". For (in any case) the random string could have a subset of size 30 that forms a valid English name also of size 30. Now, which one is the "right" name to be found? I suggest that you illustrate your idea through highly reducing the sizes, giving a concrete example with a short English name and a corresponding short random string such that your question could be clearly understood.
Jan
28
comment AES key and block size
@Maarten Bodewes: P.20 of FIPS-197 has "Figure 11 Pseudo Code for Key Expansion" and also notes that its "Appendix A presents examples of Key Expansion".
Jan
27
revised Q: Relevance of physical layer security to cryptography
added 1008 characters in body
Jan
27
revised Q: Relevance of physical layer security to cryptography
added 1008 characters in body
Jan
27
comment Implementing cryptosystems with various programming langauges
My personal view is highly biased. I don't know Agda, but from the little I know in general about PLs that let you do proofs they demand very much mental efforts of the programmer. However, C/C++ are IMHO too verbose, such that it is frequently not easy/efficient in code reviews to compare with the flow of the underlying ideas of the algorithms being implemented. I would say that it may be a good idea to forgo proofs and instead to first do a full implementation in a compact, less efficient PL like Python and after a thorough review do, if needed, "comparable" implementatons in efficient PLs.