Practicing privacy: Encryption

http://matt.might.net/articles/practicing-privacy-encryption/

52 19 13 years ago

matt.might.net

chacham15• 13 years ago

By long, I mean greater than 16 characters, and perhaps longer than 20.

Talk about going overboard... furthermore this in combination with "Don't use words or "clever" variations on words" make it all but likely that you're going to forget your own password and write it down.

rotnewson2• 13 years ago

If you can't remember 1 password over 20 characters that you will use a lot with a password manager you probably need to change what kind of passwords you make.

Instead of "E=E<4oc^(z&kj6Snm9uy" do something like "The Brown cow jumps over the m00n!".

Set the password manager to make you enter the password if you haven't used it for 30 seconds (for a few days so you remember your password).

You're using a password manager with a good password that is easy to remember but the you do use the password manager to generate hard to remember passwords like the one above.

dmix2• 13 years ago

https://xkcd.com/936/

dllthomas5• 13 years ago

Do not give password advice without looking at the entropy.

Estimates of the entropy of English text place it below 1.5 bits per character. "The brown cow jumps over the moon." would, generously, have about 34 * 1.5 = 51 bits of entropy, plus a few more for the simplistic substitutions - say 70 bits total? This is assuming the sentence was, in fact, chosen uniformly across English sentences, which is obviously not going to be the case (this one being a modification of a line from a nursery rhyme), so in actuality it'll be even worse.

A fully random password of length 20, from characters on a typical keyboard (say 94, it seems to be on mine) would have 20 * lg(94) > 20 * 6.5 = 130 bits. But impossible to remember and a pain to type correctly.

Picking from my /usr/share/dict/words with no restrictions (99171 entries), it would take 70 / lg(99171) = 5 words to be stronger than the sentence and 130 / lg(99171) = 8 words to be stronger than the gibberish, with no substitutions or tweaks, however not all of those passwords could be typed on my keyboard.

Restricting /usr/share/dict/words to those which match (with LANG=C) '^[a-zA-Z]\{1,10\}$' yields 61078 words at about 7.3 bits of entropy per word, so you would get security comparable to the above with 5 (again - aliasing) and 9 words respectively.

Some nine-word passwords generated this way:

    embryo distressed Ramadan chocks broaching official outstript explicit formulas
    tokens bruskly realizing rubric earmarks aphorism sweeps hallelujah Bardeen
    respects jocularity crummier leave spinsters Rodriquez hatch assurance torture
    patinas Elba dairymaids blabbing kissing handyman Ind tobogganed directed
    mossy Flora concepts medalist kidding heinously deafened evaluation nodes
    Steinmetz lizard Janette scatted cunning geckos belched demurring grandest
    faints nicest unleashes navel Monroe frostbites Pl loon careening
    overtake tasselled quahog utters Upjohn incloses punchy Jericho reveille
    sicked sinning premiere Satanism loiters accrual Caspar infatuate renewable
    dinning hereabouts Lithuanian formalism voiceless demoted bundle teed fluent

The above were generated with LANG=C grep "^[a-zA-Z]\{1,10\}$" /usr/share/dict/words | rl --reselect -c 10 | xargs

This is, obviously, reliant on an assumption that rl produces cryptographic level randomness, which is probably not the case but should certainly be near enough the case for examples (and in any case will be much, much closer to true than any method involving humans - we are very poor sources of cryptographic entropy).

DanBC• 13 years ago

make it all but likely that you're going to forget your own password and write it down.

Writing down your password is usually less risky than picking a weak password.

As always, assess the risks.

dmix2• 13 years ago

For cloud services I'd recommend Lastpass (works with Yubikey 2 factor) for password management and Tarsnap for backups.

mike-cardwell• 13 years ago

Worth pointing out that if you use LastPass and the US government wants a list of all of the accounts you use, a history of when you logged in to them, the IPs you were using when you logged in, and your usernames and passwords, they can get it.

All they need is a court order to compell LastPass to target your account with some modified backdoored JS. They have done this before to force Hushmail to send backdoored java applets to targetted users.

I used LastPass for a very short time. I now use a PGP encrypted text file.

pampa• 13 years ago

PGP encrypted text file is not very convenient. Give keepass a try http://keepass.info/. Its open source, cross platform and has a nice random password generator. Can't live without it.

I never understood why people would want to use a cloud-based password manager. I find the whole idea of giving your passwords to a 3rd party ridiculous, and doesn't matter if they are encrypted or not. Wasn't there a security breach with one of these services a few months ago?

dllthomas5• 13 years ago

"Encryption makes privacy a right that can be claimed rather than granted."

Not really, or at least not alone. There will always be points at which information must be encrypted. Encryption just pushes the need for the right to be granted to those points. This is not at all a bad idea, of course; just that government recognition of a right to privacy is still important.

geal• 13 years ago

Encryption provides a good way to keep secrets. This has nothing to do with privacy. Privacy is minding my own business without anyone watching me or judging me.

If you need to rely on encryption to protect your privacy, then you have very little privacy, because everything that is not encrypted can be snooped on: where you are, who you talk to and about what (because GPG doesn't protect the username and subject), who are your friends (because you can't trust them to encrypt properly).

If you want to escape surveillance, encryption is just one tool. What you really need is good opsec habits. See for examples http://fr.slideshare.net/grugq/opsec-for-hackers

dllthomas5• 13 years ago

Excellent resource, thank you for sharing it. I think we're agreed, though, that we shouldn't be needing to practice opsec to have some basic privacy.

Zigurd• 13 years ago

That recognition will no doubt come sooner the less value can be extracted from snooping.

dllthomas5• 13 years ago

Agreed. Both using encryption and pushing for better privacy protections are important and complementary.

Practicing privacy: Encryption

Related Stories