On Jul 13, 2018, at 3:13 PM, Warren Young <war...@etr-usa.com> wrote:
> Now paste in an equivalent number of ‘a’ characters, and you get 0 bits of 
> entropy.  Strictly speaking, you get 1 bit of entropy for the whole message, 
> but it shows 0 because the calculator is rounding the result off to 3 
> significant figures.

Hmmm…we also need something like a run-length prefix to reconstruct the 
message, so this calculator is undershooting slightly.

For example, 100 a’s requires a 7-bit run-length plus zero bits for our only 
code point, so we should get 0.07 bpc, within this calculator’s apparent 
precision even without dealing with roundoff errors.

Still, it’s good enough for our purposes here, which is to make it clear to us 
that if you use a hex string as a passphrase, you need 128 characters of it to 
fully justify the use of 256-bit symmetric encryption.
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