Reputation
517
Top tag
Next privilege 1,000 Rep.
See votes, expandable usercard
Badges
4 9
Newest
 Enthusiast
Impact
~14k people reached

  • 0 posts edited
  • 0 helpful flags
  • 16 votes cast
Apr
27
comment Searchable Encryption with Substring Search
My layman's question: Could your goal be exactly realizable at all for materials that are encrypted by sufficiently strong algorithms? (Do I understand correctly that you want to have a way to check whether a possible string guessed from context, say "Execute Plan B!", is in the plaintext corresponding to a given ciphertext?)
Apr
24
awarded  Enthusiast
Apr
20
reviewed Approve Updating the seed key of a PRNG while maintaining initial entropy?
Apr
20
comment Turing's (still?) classified inference engine algorithm?
To my knowledge there is since many years a museum at the cite where Turing worked and attempts were done to do some reconstruction of devices employed there in WWII. The people there are presumably able to give you a competent answer to your question.
Apr
20
revised Updating the seed key of a PRNG while maintaining initial entropy?
added 65 characters in body
Apr
19
revised Updating the seed key of a PRNG while maintaining initial entropy?
deleted 13 characters in body
Apr
19
answered Updating the seed key of a PRNG while maintaining initial entropy?
Apr
18
comment Given a public-key encryption and signature scheme, define a new primitive
I couldn't do your assigned work but simply want to say that I have written a code that employs RSA to do encryption on plaintexts directly and with integrity check as well as signature of the sender. See Ex. 3S of Appendix in s13.zetaboards.com/Crypto/topic/7234475/1/
Apr
17
comment Homomorphic Encryption or not
Your last comment means that you simply want a very simple encryption scheme. But it unfortunately follows that the security of your scheme would be very low or negligible. Cf. the ubiquitous Principle of No Free Lunch. Extending the example that you have provided yourself, a permutation polynomial mod 2**n could be of use to you, since it bijectively maps blocks of n bits. However, the secret key hereby involved, namely the coefficients of the permutation polynomial, could be recovered by the adversary, if he manages to know a correspondingly small number of pairs of plaintext and ciphertext.
Apr
15
comment How to attack polyalphabetic affine cipher with only ciphertext?
Each pair of (a,b) results in a mapping from the alphabet in the normal order to the alphabet in another (permuted) order. So if your alphabet is of size m and you have n unknown pairs of (a,b), this means that you have a poly-alphabetical substitution matrix of m*n with permuted columns that you don't know. But this is a general challenge for analysis certainly much more difficult than the classical Vigenere. It's unlikely IMHO that someone would be able to provide you a recipe to straightforwardly solve the problem.
Apr
15
comment How to attack polyalphabetic affine cipher with only ciphertext?
If you know the values (a,b) that are used to encrypt the individual letters of a given sequence, why couldn't you do the corresponding decryption?
Apr
12
comment Generating cryptographic-quality 1/f noise
A question of curiosity: If you already have a white noise, for what purposes of cryptography do you want to derive from it a pink noise?
Apr
11
comment RSA encryption with private key, decryption with public key (again)
@probaO: I believe I have correctly understood your requirement. What you need is simply to process your message with your private key. Since you securely protect your private key, other people (or machine), after having decrypted the message with your public key and found that the message is meaningful, they can be certain that that message is genuinely from you. If the recipient is a machine, i.e. in case of an application running on it, it certainly can't decide on "meaningfulness" of the text. One way out is e.g. to put a certain keyword at the end of the message so that it can check that.
Apr
11
comment RSA encryption with private key, decryption with public key (again)
@MaartenBodewes: I was telling proba0 "merely" that in the "general" case of key generation (i.e. one doesn't employ (3,n) etc. from the very beginning) the 2 key pairs resulting, (e,n) and (d,n) can be used either as public and private or as private and public and that that "choice" is entirely free (i.e. not "determined" by the key generation process as such), no more nor less! (That is, I don't see anything wrong in what I told proba0. How he actually uses his (thus chosen) public key and private key to achieve his intended purposes is his own business.)
Apr
10
comment RSA encryption with private key, decryption with public key (again)
From the outset, there is yet no distinction between private and public at all. After having generated the modulus n, I try some random value e that satisfies certain desirable criteria and then try some random value d that satisfies both certain desirable criteria and the condition well known in RSA such that (e,n) and (d,n) can be the public key and the private key, or the other way round, namely private key and public key. As said, this means that e and d are random and one does not employ particular values (3, n), (65537,n), etc. See my software s13.zetaboards.com/Crypto/topic/7234475/1/
Apr
10
comment RSA encryption with private key, decryption with public key (again)
In the "general" situation, RSA key generation gives you two pairs (e,n) and (d,n). Which pair you designate as the public key and which as the private key and handle them accordingly (the one you let others know, the other you securely protect) is "absolutely" your freedom. Only for certain practical (i.e. processing efficiency) reasons one often perfer to have one of them be very particular in nature, e.g. (3,n) and in that case that one should obviously be the public key (and not the other way round.)
Apr
9
comment Is pseudo-random letter insertion secure?
To the last questiion of your OP: If my memory doesn't betray me, employment of dummies to confuse the adversary is a known technique in classical crypto. Anyway, my browsing happened to turn up a post of a recent proposal in that direction, see Post #13 of macosx.com/threads/simple-encryption-with-strings.36401
Apr
9
answered RC6 Key Size Understanding
Apr
6
comment What problems with “random” data would cause this result from Ent?
Applying the common entropy formula to one's data straightforwardly is anyway problematical IMHO. Cf. crypto.stackexchange.com/questions/33231/entropy-calculation
Apr
3
comment What asymmetric key exchange algorithms are known besides DH?
My layman's question: If an adversary is capable to tap exactly all bits that are being transferred between the communication partners, wouldn't he be able to employ the same "reconciliation" mechanism to obtain the common secret key?