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Feb
2
comment Is AES in CBC mode secure if a known and/or fixed IV is used?
@juwiley I would suggest wikipedia's Mode of Operation article as a first start, it has many more links.
Jan
17
comment Are there any advantages in using proprietary encryption?
I wouldn't call it "state of the art" to use an proprietary (i.e. not widely analyzed) algorithm. Maybe "cutting edge" is more correct (and even sounds cooler).
Dec
22
comment AES - What is the advantage of a 256-bit key with a 128-bit block cipher?
Actually, for three elements there are only $6 = 3!$, not 9.
Nov
25
comment Public key crypto instead of hashing passwords in a database
public-key encryption is usually not deterministic, so you can't really use this to check if the password matches.
Nov
13
comment Private and public keys, how do they relate mathematically?
Also, please have a look at the questions linked at the side bar under "Related" ... I guess some of them might answer your question.
Nov
12
comment Why can't I reverse a hash to a possible input?
Basically, all currently known hash unbroken functions are just "nobody knows how to break them". I don't think any of them has a complete proof. (Some have partial proofs showing that they are "secure" (in some formal sense) if some component is "secure" (in the same or another formal sense)).
Oct
25
comment Should I use ECB or CBC encryption mode for my block cipher?
@Imray I guess when your data is smaller than one block, and will not repeat anyways (i.e. already includes a nonce), and you are really space/bandwidth-limited, ECB has some uses. Might have other ones I'm not aware of.
Sep
1
comment How does the index of coincidence work in the Kasiki test?
No, it depends on the text being typical enough (i.e. having a typical distribution of letters for the language being analyzed), and long enough.
Aug
30
comment Webcam random number generator
@PaulUszak does it say anything about JPEG? The webcam could give you pure uncompressed image data, which you can subtract. (The web page doesn't seem to be available anymore.) I also don't see how treating the whole JPEG file as one entropy source makes stuff better.
Aug
20
comment Combining several symmetric ciphers using XOR
You might want to mention that for this to be secure, both ciphers must be sufficiently non-similar so they don't cancel each other out, or have independent keys, preferably both.
Aug
20
comment Combining several symmetric ciphers using XOR
Please don't use the word "one-time pad" for a stream cipher. This is not the same.
Jul
12
comment How is an epsilon of 1/1000 non-negligible?
Could you elaborate on this? As it is, it doesn't answer the question at all.
Jun
13
comment Encryption of exe file
Encryption works on anything, not just "text".
Jun
6
comment Are there security issues with adding plaintext length to TLS packets?
Note that your changed protocol will not be compatible to TLS anymore.
Jun
6
comment Share two secrets between two parties
Welcome to Cryptography Stack Exchange. We actually prefer answers which contain the information itself, not just referring to information elsewhere. Could you add a summary of the information to the answer? Otherwise we will convert your answer to a comment.
May
28
comment Is it practical to use a stream cipher in a block cipher mode?
Actually, my answer didn't say "you can't convert a stream cipher into a block cipher", but "the way of converting which was proposed in the question doesn't work". I'll try to edit it.
May
27
comment Effective security of block cipher – equal the key size, or half the key size?
@Dillinur If I remember right, there is a generic quantum algorithm which finds preimages to functions in $O(\sqrt{N})$ time, where $N$ is the number of possible candidates (i.e. $O(\sqrt{2^n}) = O(2^{n/2})$ for $N = 2^n$). Of course, for this to actually work, you need a quite large quantum computer (about $n$ qbits, I think), and also fast enough. Then it depends on the constant factor to see if it is faster than regular brute-force.
May
27
comment Effective security of block cipher – equal the key size, or half the key size?
Also, this only seems to work with a fixed initialization vector (or if you somehow manage to query the block cipher itself), right? (I guess a "chosen-IV-fixed-known-plaintext" attack on CBC allows this.)
May
27
comment Effective security of block cipher – equal the key size, or half the key size?
Maybe the algorithm would be clearer if the first loop used $X$ instead of $T$ as a variable name? (Also, the hash table access is likely not O(1), but $O(\log(2^{n/2})) = O(n)$. Still almost negligible compared to $O(2^{n/2})$.)
May
26
comment Effective security of block cipher – equal the key size, or half the key size?
@J.D. Please add this as an answer (with some details of how this attack works and a reference to a paper or similar).