Recovery phrase (mnemonic) length

[sondreb]

The node UI will now generate a 24 word recovery phrase (mnemonic), perhaps this should be a user option and allow users to use 12 words if they want to?

[dangershony]

After thinking about this more I think its a good idea to allow 12 words.
While it perhaps has less entropy it's still enough

Mainly the benefit is the ability to remember the mnemonic which in some cases/users is more secure then storing it somewhere on disk or usb or safe.

So we should provide that option.

[soma42]

yes, so since blockcore serves a wide range of people, 12 and 24 should be supported...lets just hide the 'BIP-0039-Passphrase' under "advanced" or so.