I was playing around today with the easiest way to remember 128 bits for a private key.

The nicest way I have seen so far is from etotheipi (IIRC) which was:

Choose 8 words from a vocab list of 2^16 (= 65536) words.

This gives 8 * 16 = 128 bits of entropy.


I looked at various sets of things and how easy they were to remember and think countries is quite useful.
It is a little nebulous the definition of a country but let's use the US State department's list of 195 countries. This gives 7.6 bits per country choice.

To get 128 bits of entropy you can then use:

6 choices of a country plus a word from a vocab list of around 13700.

You can have a simpler vocab list, which could concentrate more on concrete things.
To remember the full 128 bits for a private key you might have to memorise a list:

cat from Benin
umbrella from Guatemala
pomegranate from Canada
brick from Malaysia
sausage from Australia
roof from Mongolia

To make best use that our memories are associative, you would first remember:

cat
umbrella
pomegranate
brick
sausage
roof

These have to be remembered in order. I suggest these are just remembered by rote or by a little 'nonsense story'. (The cat walked past the umbrella and saw a pomegranate sat on a brick. Then some sausages fell off the roof).

And then you would need to remember:
What country was the cat/ umbrella/ pomegranate/ brick/ sausage/ roof from?
You could do this be imagining, say,  a shocked Canadian mounty holding a pomegranate, the Sydney harbour bridge made out of sausages or whatever.

Do people think this is an easier way to remember 128 bits?