Timeline for Securing a prediction about a future event
Current License: CC BY-SA 3.0
7 events
| when toggle format | what | by | license | comment | |
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| Apr 21, 2015 at 13:58 | comment | added | Tom Leek | Length does not provide entropy. It merely provides room for entropy. The "80 bits" value is the traditional limit of computational feasibility, though the relentless increase in computational power of computers should warrant, at some time, a new traditional limit (cryptographers being in love with powers of 2, they now often talk about "128 bits" as that absolute limit). | |
| Apr 7, 2015 at 3:55 | comment | added | Daniel H | @TomLeek Isn’t it also a function of length? Longer the messages have more entropy. If you were to predict the weather in the 100 most populated cities, your prediction couldn’t be brute-forced even if the attacker knew that’s what you were doing. Alternately, if you were to hash a patent application for proof of anteriority, the number of possible wordings is such that padding is unnecessary even for an attacker who knows exactly how the device works. I’m also not sure where you got the 80 bits number. Could you look at my question (security.stackexchange.com/q/85388/71892) about it? | |
| Feb 4, 2014 at 1:07 | comment | added | Darren Cook | Regarding your last point about keeping it in your head; the original string could be encrypted (e.g. a gpg email sent to yourself) (?) | |
| Jan 30, 2014 at 20:04 | vote | accept | William Breathitt Gray | ||
| Jan 30, 2014 at 19:56 | comment | added | Tom Leek | The random padding is useful only if the attacker has a non-negligible probability of finding the exact prediction text when he tries "potential predictions". It is not a question of length but of contents. In practice, we have to assume that if the attacker is interested in cracking the prediction, then he knows some context information about it, which can help him narrow his search. The random padding guarantees an absolute bound to this "narrowing". | |
| Jan 30, 2014 at 19:24 | comment | added | William Breathitt Gray | Suppose an attacker has no information about the prediction -- that is, they simply receive the hash and knowledge that it was computed from a text file. Would the random padding no longer be necessary, since the length of the text is not known (as far as the attacker knows, the hash could have been derived from the concatenated sentences of an entire library)? | |
| Jan 30, 2014 at 18:10 | history | answered | Tom Leek | CC BY-SA 3.0 |