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seen Oct 18 '13 at 10:54

Oct
18
comment Are there any hand ciphers not obsoleted by computer cryptanalysis?
@WilliamHird A scenario would be a journalist investigating abuses in a totalitarian state. Journalist generates a series of one-time pads (literal pads) and keeps a photocopy/scan of them in a secure bank vault in their democratic home country. While taking interview notes and other observations in the totalitarian state, each note is encrypted with a one-time pad which is then burned. Once the journalist gets home, they can decrypt their notes. You'd probably also want physical hiding techniques for the pads and the encrypted notes.
Oct
18
comment Is there any strong enough pen-and-paper or mind cipher?
+1. As the question didn't mandate you had to remember the key in your head; and 'cipher' terminology excluding one-time-pads is splitting hairs for this question.
Oct
13
revised How exactly is “true randomness” defined in the realms of cryptography?
short version of answer
Oct
13
comment How exactly is “true randomness” defined in the realms of cryptography?
If this @Tanath I assume you are going to comment on the down-vote.
Oct
13
answered How exactly is “true randomness” defined in the realms of cryptography?
Oct
12
comment How exactly is “true randomness” defined in the realms of cryptography?
I'm not sure if you are agreeing or disagreeing with the proposition ("Randomness is... etc"); so I'll put the proposition into a different answer so as not to contaminate interpretation of your answer.
Oct
10
comment Encrypting files with known headers
@PaulLynch On a side note, was this question a list question initially? I think the kerfuffle of Stephen vs Woliveirajr and I was actually regarding implicit assumptions about the question.
Oct
10
comment Encrypting files with known headers
@PaulLynch Now that this question has migrated across to cryptography.se, Gilles more in-depth answer is the most suitable for the level of detail you desire :-). In theory, as computers are linear and deterministic, block and steam ciphers differ only in whether and when working memory for avalanching is written out to the ciphertext. In practice, most ciphers are cognitive tarpits of interrelated bitwise-avalanches and best left as end-user black-boxes called 'block' or 'stream' depending on the staggering of input and output data.
Oct
10
comment Encrypting files with known headers
@StephenTouset On a side note, I rarely downvote answers, especially on any question I'm also answering - but I will apply TFT resolution to discourage casual sniping.
Oct
10
comment Encrypting files with known headers
I must clearly have sock puppets to have down voted you twice, make that thrice.
Oct
10
comment Encrypting files with known headers
A crypto-primitive is not an "encryption scheme"; of course any compliant end-user API will include IVs where applicable.
Oct
10
comment Encrypting files with known headers
Sigh. I would assume someone using an encryption scheme without subverting it at the code level would follow the scheme's initialisation process. You not referring to a plaintext attack of a single message but across messages; where we create fresh PRNGs for the same private key by adding some public random bits/IV to the stream. The IV and private key influence the entropic state equally for a properly implemented cipher; so the IV aspect is relevant across key re-use only.
Oct
10
answered Encrypting files with known headers
Oct
7
comment Is this a good entropy collector and whitening technique?
@JohnLynx I would refer you to the NIST test suite, but the current libertarian shutdown of the United States limits that option. You can download a non-authorative mirror copy from here, but without reading the unavailable NIST help guide I couldn't say how exactly you'd use it. GSL (GNU Scientific Library) is a diluted less-cryptic alternative but you'll need to install Cygwin if you are using Windows; and it requires gcc compilation because of course it does it's a #$%^ GNU app...
Oct
7
comment Is this a good entropy collector and whitening technique?
@JohnLynx I couldn't find an article on average entropy of keyboard and mice movements, so you'll need to test this yourself. Especially as entropy will usually be implementation specific. Applying randomness tests after hashing will give a false sense of randomness due to the "whitening" of the hash; so collect a lot of Step 1/2 data then run the test suite. I've no idea what the ratio would be because humans are bad at guessing randomness.
Oct
6
awarded  Commentator
Oct
6
comment How exactly is “true randomness” defined in the realms of cryptography?
(cont.) We usually address the problem of temporal causality obliquely through Brownian Motion a/k/a massively parallel temporal causality - where the causality information is lost through collapsing the temporal reference frames down from N actors to 1 observer. The avalanche in a PRNG works in much the same fashion. If this isn't what you meant in your answer, would you like me to create this as a separate answer? (My earthquake/sunspot example was limited in retrospect as all inherent causality was not removed.)
Oct
6
comment How exactly is “true randomness” defined in the realms of cryptography?
Think of it this way: Every random event may be causal as far as we know. If so, sources we attribute as random a priori are simply streams of related events with the information regarding the causal relationship deleted. We can say "ah ha but I see a pattern" but this means we didn't delete enough of the causal information packaged with the event. One form of pre-packaged causality that is so common we rarely think about it and is also stubborn to delete (since our own action of deletion requires the selfsame causality) is Temporal Causality.
Oct
6
comment What is adversary's advantage in cryptography and why we use it?
Google's cache refresh for Stack Exchange is impressive. I wonder if we're getting special love from Google or our site is simply that popular to warrant a fast cache refresh?
Oct
6
revised Is this a good entropy collector and whitening technique?
more advice for step 1