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Dec
14
comment How to apply linear cryptanalysis to PRESENT?
Your question seems quite broad to me, and you might want to narrow it down a bit. While I might be wrong, I don't think anyone's likely to post a complete walkthrough of cryptanalysing PRESENT here, and in any case, it might not even fit in our answer length limit. However, if you could tell us how much you've figured out on your own, and where specifically you're getting stuck, that might increase your chance of getting useful answers.
Dec
14
comment Is symmetric encryption vulnerable to plain-text-attacks?
@David天宇Wong: That's basically what adding a message authentication layer does: it makes the probability of a successful decryption oracle query (on a message not previously obtained from the encryption oracle) negligible, and thus effectively makes the CCA game identical to the CPA game.
Dec
13
comment What are the negative consequences for choosing 8 S-boxes for DES vs 1 S-box for AES?
I'd guess mostly implementation complexity.
Nov
26
comment How to check if a function is significant or not?
@user3193259: How did you "see" that it's not reaching zero? Just by plotting? That can be quite misleading for slowly converging functions. Instead, you might want to try solving the equation $x = 1/(\log n)^{1/2}$ for $n$ as a function of $x$.
Nov
26
comment Why is PuTTYgen-created RSA public exponent(e) not in {3,17,65537}?
According to The Jargon File, 37 is the most common answer when people are asked to pick a random number from 1 to 100. No citation, though. :(
Nov
26
comment Decoding base64 encoded message with a key
Note that many programming languages / environments include a built-in tool for such character replacement, e.g. tr/// for Perl, strtr() for PHP, string.translate() for Python, etc. Many of these are modeled on the Unix command-line tool tr. In particular, to decode your example string using Unix tools, just run the command echo ucaUCo4NmA88Tws8BoQsKAXdBcDn | tr 'gP9jOzA75VyIW6FRuHZimQcLB1rCTKpGN8hdEXw0eY3kMx+/JDUntsob4a2qfSv' 'A-Za-z0-9+' | base64 -d.
Nov
21
comment For AES CBC, can I encrypt the IV with AES ECB and the same key and include it with the message?
Related: Why is the IV passed in the clear when it can be easily encrypted?
Nov
14
comment Does complicating a flawed algorithm make it secure?
Related: What is the actual difference between security through obscurity and true encryption? and Why should I make my cipher public?
Nov
5
comment Is it possible to correct the exponent of an RSA public key if it has been altered?
@aadithvmenon: No, that wouldn't really be on topic here. In any case, you're presumably meant to solve the puzzle yourself. You could maybe ask for hints in chat, but you need a few more rep points to get full access to it. (And of course, there's still no guarantee that anyone will actually feel like taking the time to help you.)
Nov
5
comment Is it possible to correct the exponent of an RSA public key if it has been altered?
If you've only got the public key and the message, then you won't be able to decrypt anyway, regardless of whether you correct the exponent or not. Unless, of course, "taken wrongly" means that the person who encrypted it did something silly like encrypt with the decryption exponent, in which case... well, it should be obvious what to do. :-)
Nov
5
comment Is it possible to correct the exponent of an RSA public key if it has been altered?
"Just a text file" doesn't really tell much; a lot of the formats for storing RSA keys are text files (often containing a bunch of base64-encoded data). If it starts with a line like ---- BEGIN (whatever) ----, Google for that line to see what type of key file it is. If it starts with something like <RSAKeyValue> and has lots of angle brackets in general, it's probably in XKMS format. If it's just got two numbers (a large and a small one), well those are probably the modulus and the exponent.
Nov
4
comment Is it possible to correct the exponent of an RSA public key if it has been altered?
That depends on the key file format you're using.
Nov
2
comment Developing algorithm for detecting plain text via frequency analysis
This is essentially what the OP did before, using $n$-gram frequencies. Alas, if one is only looking at every $k$-th letter in the text, for $k \ge 2$, such pairwise correlations are not very useful.
Nov
2
comment Many time pad attack
@AutonomousApps: Look at the "bin" column in the table you linked. Note that bits are conventionally numbered from right to left, with bit 0 being the rightmost (i.e. the numerically least significant) bit.
Nov
1
comment How is bitslicing faster?
@fgrieu: Honestly, I've no idea. It's been a while since I've done any actual assembly coding myself. I just suggested those as vaguely plausible examples of oddball instructions that could be useful.
Oct
29
comment How is bitslicing faster?
@Thomas: If Galois fields are on topic, I'd say bitslicing is, too. Sure, you could ask this on SO, or perhaps dsp.SE, too, but the answers you'd get there would likely have a different emphasis than what you'd get here on crypto.SE. IMO, like the Galois fields question, this one falls into the legitimate area of overlap between different sites. There have been quite a few papers published in crypto journals about bitslicing; I think that's enough to make it on topic here too.
Oct
28
comment How is bitslicing faster?
Anyway, if all you'd like is some more descriptions of the technique, perhaps the original paper on DES bitslicing (Biham, 1997) or this paper on AES bitslicing (Käsper & Schwabe, 2009) may be useful.
Oct
28
comment How is bitslicing faster?
I'm sorry if I'm being unreasonably suspicious, but what you've written above sounds just a little bit uncomfortably like a "please answer my homework assignment for me" question. If this is not, in fact, the case, it might help if you could provide a bit more context for your question, and perhaps specify what exactly about bitslicing you're having trouble understanding.
Oct
27
comment How is digital signature different from a message authentication code (MAC)?
+1; also, the deniability of MACs may sometimes be considered a desirable property, e.g. for encrypted private communications where you may not wish to leave the other party with a permanent proof of what you said to them.
Oct
27
comment How is digital signature different from a message authentication code (MAC)?
...and then there's also What are the differences between a digital signature, a MAC and a hash?