On 07/24/2013 10:32 AM, Kent Borg wrote:
I don't know current estimations, but I would use the following
guidelines for an encryption key:
32-bits of entropy: stops a naive individual with a day-job
80-bits of entropy: stops a small organization
100-bits of entropy: stops a big organization
128-bits of entropy: stops the NSA
256-bits of entropy: paranoid's goal
Reading a New York Times story on Snowden contacting the film maker
Laura Poitras, Snowden is quoted as advising a strong passphrase:
"Assume your adversary is capable of a trillion guesses a second."
Interesting. So they can brute-force an entire 32-space in a fraction
of a second and a 64-bit space in a bit over a half a year. But an
80-bit space can't be completely traversed in 38,000 years. Even if the
NSA is really really angry and the president says to get the
bastard...just 80-bits is pretty dang good.
I guess I left some room for error in the above.
-kb
P.S. Again, estimating entropy by looking at a passphrase is a doomed
exercise. The only way to know the entropy of a passphrase is to know
how it was generated and count many random decisions were made driving
that process.
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