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seen Aug 25 at 20:26

I am a math/computer nerd. Nothing to see here, move along.


Aug
25
reviewed Close Seemingly simple decryption question
Aug
25
reviewed Close Counter Mode: how to choose the nonce part of the counter?
Aug
25
reviewed Close Solution with high decryption cost and low encryption cost
Aug
23
comment Efficiently map $2^n$ unique 64-bit vectors to $2^n$ $n$-bit vectors where $n < 64$?
I'm not sure what you're arguing. For concreteness, let's use the example I gave earlier, and suppose that, say, n = 63, both x1 and x2 are at least 2^63, x2 = DES_K(x1), and suppose that y = DES_K(x2) < 2^63. My understanding of your proposal is that both x1 and x2 would map to y because this is the first value in [0, 2^63) we reach by repeated application of DES_K, regardless of whether we start from x1 or from x2. If this is incorrect, could you please clarify how the mapping is computed?
Aug
23
comment Efficiently map $2^n$ unique 64-bit vectors to $2^n$ $n$-bit vectors where $n < 64$?
The "cycle-walking" method wouldn't work here because your target space is not your source space. For example, you could have two inputs X1 and X2 in your source space such that AES_K(X1) = X2 (it would make slightly more sense to use DES here, but same thing would happen). In this case, X1 and X2 would then map to the same point in your target space, unless X2 was already in it.
Aug
22
reviewed Leave Open mixing SPN and Fiestel
Aug
22
reviewed Leave Open Rely on NSA Suite B Cryptography?
Aug
15
awarded  Yearling
Aug
7
revised Is it insecure to encrypt the wrong plaintext?
added 140 characters in body
Aug
7
answered Is it insecure to encrypt the wrong plaintext?
Aug
5
comment How many degrees of freedom up my sleeve?
You might find the (satirical but still substantive) paper "How to manipulate curve standards: a white paper for the black hat" interesting; it addresses this question in the context of ECC parameters. PDF: eprint.iacr.org/2014/571.pdf
Jul
22
reviewed Approve suggested edit on How do we compute IV+1 in CTR mode?
Jul
21
comment Lowest number challenge scheme
This is Yao's Millionaires' Problem: en.wikipedia.org/wiki/Yao's_Millionaires'_Problem
Jul
3
answered Pseudorandom permutations on domains of arbitrary (i.e. not a power of 2) size
Jun
19
reviewed Approve suggested edit on Modes of Operations Exercise
May
28
comment AES/CBC fixed Initial vector use-case
Using a fixed IV will also leak the information about the length of any shared prefixes. Also note that CBC won't stop someone from tampering with the cookie so that it decrypts to something that you don't expect, and if an attacker can guess at some of the cookie's contents, he will have a degree of control over what this is.
May
27
awarded  Enlightened
May
27
awarded  Nice Answer
May
24
awarded  Enlightened
May
24
awarded  Nice Answer