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On Thu, 25 Mar 2010 15:23:52 -0400 (EDT) |
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lists@×××.org wrote: |
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> Right, he simply turned /dev/random into /dev/urandom. |
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> I was under the impression the entropy key was simply a fancy PRNG. |
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> Now that I know it offers true randomness, I'm more impressed. Also |
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> curious exactly what it uses as a source. |
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From http://www.entropykey.co.uk/tech/: |
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"The Entropy Key uses P-N semiconductor junctions reverse biassed with |
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a high enough voltage to bring them near to, but not beyond, breakdown |
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in order to generate noise. In other words, it has a pair of devices |
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that are wired up in such a way that as a high potential is applied |
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across them, where electrons do not normally flow in this direction and |
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would be blocked, the high voltage compresses the semiconduction gap |
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sufficiently that the occasional stray electron will quantum tunnel |
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through the P-N junction. (This is sometimes referred to as avalanche |
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noise.) When this happens is unpredictable, and this is what the |
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Entropy Key measures." |
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It's a pretty standard trick. What's special is that it uses two, and |
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mixes the contents together, and so it can detect when one fails. Oh, |
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and its price. (Other, much less sophisticated devices, cost as much |
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as ten times more and are toys in terms of their security against |
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attack.) |
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B. |
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