# Tag Info

6

As pointed in this comment, using a huge random key for a sound block cipher is an excellent defense to resist ASIC/GPU attacks. Each bit added doubles the effort required. If an adversary was able to build $10^{12}$ ASICs each capable of testing $10^{12}$ keys per second, odds of finding a 128-bit key by brute force running that for a decade are less than ...

5

A video camera can obtain entropy, but only at a fairly low rate and only if allowed to see "unusual" scenes… like someone making funny faces, unusual movements, etc. Of course, this only works in a room with no video bugs. Theoretical explanations… Depending on your knowledge-range, the following sources may be able to explain ways webcams can be used ...

4

No, you will not be ble to abuse challenges in that way. You may be thinking about e.g. raw RSA, where signing and decryption are mathematically similar. However, this is not possible in FIDO U2F: All the defined signature algorithms use SHA256 on the signed data, meaning that you'd have to brute force search for something that produces the correct ...

3

The access codes were recently leaked (by whom, I don't know). My Yubikey is listed and I can confirm that the access codes were necessary and sufficient to reprogram it. You can change or remove the access code as part of reprogramming too. The leak doesn't make the Yubikeys useless in the extremely unlikely event of Gox rising from the flames — no ...

3

Don't think you've missed something. How do they keep these systems from being broken by someone just looking at the information in the smartcard that houses the key? Those systems have indeed been (and frequently are) broken via Hardware reverse-engineering. Therefore I would chime in with your "not secure". OTOH: decrypting AV signals isn't like ...

2

First, you should not write your own CSPRNG - there are plenty of well vetted ones from which you may pick. Second, your text and your pseudo code do not match (rotate key or rotate the seed). Third, as I understand this algorithm it doesn't even give good randomness properties. For example: Main> let seed = `0x82398eeaf74239 : [64] Main> let key = ...

2

At one point, most music legally sold digitally was protected by DRM (all iTunes music, for instance). Eventually the labels backed down and started allowing the music to be published DRM-free. So yes the music industry has attempted this, but it encountered all of the fundamental problems with DRM and was abandoned. Crypto fundamentally can't protect you ...

1

NIST has a lot of information on testing random number generators at http://csrc.nist.gov/groups/ST/toolkit/rng/index.html that might be of value to you.

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