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seen Aug 18 at 23:20

Aug
22
comment Dictionary attack on pass-phrases on common algorithms
Except that XKCD is showing a four word pass phrase at 44 bits of entropy by choosing 4 words from a 2^11 entry dictionary. He's not saying it's more secure because of the plain string length.
Aug
22
comment Is digest=HASH(HASH(a)+HASH(b)) equivalent to publishing two digests?
They're only 20 bit strings. You can sort those even in a language without loops.
Aug
22
awarded  Scholar
Aug
22
accepted How long would the 100 Year Cryptography Project have secured its data had it been started 100 years ago?
Aug
22
comment Dictionary attack on pass-phrases on common algorithms
@gokoon English is, effectively, a small list of words.
Aug
18
comment How long would the 100 Year Cryptography Project have secured its data had it been started 100 years ago?
The point about things being qualitatively different back when crypto was all military secrets is well-taken. Nevertheless, world-class experts were certainly collaborating in teams within the scope of their own secrecy, which could still be quite impressive. (Bletchley Park cf. Eurocrypt 2011 anyone?) Collaboration in a restricted scope certainly has disadvantages, but being well-funded and focused has its own advantages too. Is it any more unfair of a question to them than to those attempting such a project today? Maybe, perhaps.
Aug
18
comment How long would the 100 Year Cryptography Project have secured its data had it been started 100 years ago?
For a question that cannot be answered, I found that to be a pretty interesting answer. :-) It was intended to be a bit ambitious and open-ended.
Aug
18
awarded  Student
Aug
18
asked How long would the 100 Year Cryptography Project have secured its data had it been started 100 years ago?
Aug
18
comment Are these emerging threats against AES affecting your designs?
I think the "100 year crypto" concept is cool enough that it should be exempt from the usual advice about appropriately-sized functions. Isn't that sort of the point? Hmm, I think I'm going to open a question about this...
Aug
18
revised Are these emerging threats against AES affecting your designs?
updated
Aug
17
answered Is there an algorithm to find the number of intersections of two sets?
Aug
17
answered Are these emerging threats against AES affecting your designs?
Aug
16
answered Why does PBKDF2 xor the iterations of the hash function together?
Aug
16
awarded  Citizen Patrol
Aug
14
awarded  Enlightened
Aug
14
awarded  Nice Answer
Aug
11
comment How should I calculate the entropy of a password?
@this.josh If you expect the attacker to expect you to use some positions more than others, yes. Whether or not that's a good expectation is an interesting discussion. There is said to be a government agency using a password restriction of "if there is only one letter or special character, it should not be either the first or last character". I wrote a blog post a while back on this extendedsubset.com/?p=18
Aug
11
comment How should I calculate the entropy of a password?
Perhaps you could put it like this: entropy exists from the perspective of some party. To the user who knows their password, the password has zero entropy. But usually the party we're discussing the entropy is some hypothetical attacker. If you were to show him the password one symbol at a time, how much new information (in units of bits) would he learn as he sees each one arrive in turn? So the entropy is about the generation of the password insofar as we expect the attacker to know the method, but not the values, of that generation process.
Aug
11
comment Properties of PRNG / Hashes
So I was right that NIST wouldn't like "a1 = hash(seed), a2 = hash(seed + a1), ...", their approved method is somewhat more complex and does involve counters. I was wrong thinking that NIST wouldn't like a recursive SHA-1 PRNG at 160*2^80 bits output, AFAICT they don't allow anything to output more than 2^67 bits!