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lsparrish comments on Open Thread, October 13 - 19, 2013 - Less Wrong Discussion

4 Post author: Coscott 14 October 2013 01:57AM

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Comment author: lsparrish 21 October 2013 06:30:40PM *  0 points [-]

According to the Diceware FAQ, large organizations might be able to crack passphrases 7 words or less in 2030. Of course that's different from passwords (where you have salted hashes and usually a limit on the number of tries), but I think when it comes to establishing habits / placing go-stones against large organizations deciding to invest in snooping to begin with, it is worthwhile. Also, eight words isn't that much harder than four words (two sets of four).

One specific use I have in mind where this level of security is relevant is bitcoin brainwallets for prospective cryonics patients. If there's only one way to gain access to a fortune, and it involves accessing the memories of a physical brain, that increases the chances that friendly parties would eventually be able to reanimate a cryonics patient. (Of course, it also means more effort needs to go into making sure physical brains of cryonics patients remain in friendly hands, since unfriendlies could scan for passphrases and discard the rest.)

Comment author: hyporational 21 October 2013 08:32:44PM *  0 points [-]

Of course that's different from passwords (where you have salted hashes and usually a limit on the number of tries

I don't understand what you mean by this. How are salting and limits properties of passwords (but not passphrases)?

Comment author: lsparrish 22 October 2013 02:16:41AM 0 points [-]

What I meant is that those properties are specific to the secret part of login information used for online services, as distinct from secret information used to encrypt something directly.

Comment author: Douglas_Knight 21 October 2013 07:06:47PM *  -1 points [-]

Yes, there are some uses. I'm not convinced that you have any understanding of the links in your first comment and I am certain that that it was a negative contribution to this site.

If you really are doing this for such long term plans, you should be concerned about quantum computers and double your key length. That's why NSA doesn't use 128 bits. Added: but in the particular application of bitcoin, quantum computers break it thoroughly.

Comment author: lsparrish 21 October 2013 09:00:46PM 1 point [-]

I am certain that that it was a negative contribution to this site.

Well, that's harsh. My main intent with the links was to show that the system for picking the words must be unpredictable, and that password reuse is harmful. I can see now that 8-word passphrases are useless if the key is too short or there's some other vulnerability, so that choice probably gives us little more than a false sense of security.

in the particular application of bitcoin, quantum computers break it thoroughly.

This is news to me. However, I had heard that there are only 122 bits due to the use of RIPEMD-160 as part of the address generation mechanism.

Comment author: hyporational 22 October 2013 03:02:59AM 0 points [-]

I am certain that that it was a negative contribution to this site.

Rudeness doesn't help people change their minds. Please elaborate what you mean by this. Even if he's wrong, the following discussion could be a positive contribution.