security

On the 29th of August a colleague asked me “which key should I use to encrypt to you?” I was confused, because I only have one key for that email address. So he showed me the keys he saw:

$ gpg2 --list-keys --fingerprint arne.babenhauserheide
-------------------------------
pub   2048R/A70DA09E 2011-10-07 [expires: 2016-10-05]
uid                  Arne Babenhauserheide <arne.babenhauserheide@kit.edu>
sub   2048R/39829E5F 2011-10-07 [expires: 2016-10-05]

pub   2048R/A70DA09E 2014-06-16 [revoked: 2016-08-16]
uid                  Arne Babenhauserheide <arne.babenhauserheide@kit.edu>

Do you want to have secure passwords which are memorable and easy to type? Did you use diceware just to find out that the rate of typos when writing 6 words with 30 letters in total without seeing what you type can be aggravating — especially when you have to enter your password several times a day?

The algorithm here generates secure Letterblock passwords which are easy to type and to remember. Try it:

A major part of this article is concerned with a security estimate of the generated passwords, but firstoff, here’s an example of a password which should survive an attack leveraging all smartphones on the planet until at least 2021 at the current development speed of technology:

hXFV!4Vgf-LrgS

And here’s one which should outlast a type II civilization:

HArw-CUCG+AxRg-WAVN-5KRC*1bRq.v9Tc+SAgG,QfUc

Let’s ramp up security of passwords while making them easier to remember.

Update Also see Keylength - ECRYPT II report on key sizes. The report provides a clean overview of several different recommendations. In short: Use 128 bits. With the method shown here this is equivalent to using 5 blocks of 4 letters (length 20).