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26/20 answers
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 Revival
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1h
revised Does the encryption algorithm DES perform random permutations? If so how is information not lost?
added 424 characters in body
2h
comment Does the encryption algorithm DES perform random permutations? If so how is information not lost?
@fgrieu Something like this?
2h
revised Does the encryption algorithm DES perform random permutations? If so how is information not lost?
added 223 characters in body
3h
revised Does the encryption algorithm DES perform random permutations? If so how is information not lost?
added 113 characters in body
3h
comment Does the encryption algorithm DES perform random permutations? If so how is information not lost?
I don't do many descriptions of cipher design. I'll rely on the CSE community here to shoot me down if I made a horrible mistake somewhere.
3h
answered Does the encryption algorithm DES perform random permutations? If so how is information not lost?
20h
comment Is it practical to use a stream cipher in a block cipher mode?
Pretty slow but it does have a configurable block size; that counts for something I suppose. I don't directly see any application, but it is good to get a refresh on Dan's course.
22h
comment One time pad in CBC mode?
This doesn't really answer the description in the first to last paragraph, but that's probably because that paragraph does describe neither known or chosen plaintext attacks.
22h
comment One time pad in CBC mode?
@cpast well, unless I'm very mistaken there are no tags of unlimited size. OTP puts the bar impossibly high in that regard.
1d
answered One time pad in CBC mode?
1d
comment RSA public key exponent generation confusion
@fgrieu It's a good thing that that standard limits the size of the public exponent, but it would be better to have it standardized on $e=2^{16}+1$. Now every terminal (box) has to test for larger $e$ values as well. Of course, it's pretty moronic to chose a large value $e$ even if the standard allows such values (this could be a bit of a dangerous statement for me to make, but whatever :) ). Just standardizing on 1024 is a bit dangerous as well, even though I don't see anybody factor such a private key just to attack a single tacho card. You could buy a truck for that amount of money :)
1d
awarded  Revival
1d
revised RSA public key exponent generation confusion
added 183 characters in body
1d
comment Why don't we have hardware generate NON-pseudo, but REAL random numbers from meta-stable flip-flops?
Created last close vote as in my opinion the question itself isn't correct. I agree with Gilles that we do use hardware RNG's. A hardware RNG in a CPU is a very useful tool. Fortunately we see more and more CPU's include one, and those are not just embedded security chips.
1d
revised RSA public key exponent generation confusion
added 92 characters in body
1d
answered RSA public key exponent generation confusion
1d
comment Is it practical to use a stream cipher in a block cipher mode?
The question was if it was practical not possible. Although the answer of Paŭlo (with alt-gr - shift - 9 u) did not indicate this, it seems possible but not practical. From the same presentation: "Not used in practice due to slow performance".
1d
accepted Finding public exponent e
1d
comment Finding public exponent e
OK, by the way, that was for a 4Kib key. For 8Kib keys it's about 3.3 seconds, but in that case the calculation of $p$ and $q$ from $n$, $d$ and $e$ (unrelated) takes 4 times that. For completeness: this is an Intel T5670 (Core 2 Duo) ... I said old :).
1d
comment Finding public exponent e
Java is very much based on 32 bit signed integers. But I was wrong, I just tested 2^64 - 59 and that one worked too. I mistook the number of iterations with the actual number. It was pretty fast (~1s on my aging laptop) for that number as well and used only about 40K of memory, so for all practical values of $e$ the Wiener attack should suffice.