Most seeds are generated out of 5000 words as far as I know.
BIP39 (and electrum) seeds are specified with 2048 words.
Thus 20 words if its all English becomes the "safe" level against a brute force, if I do it over 3 or 4 languages does that change?
Of course, the greater your possible space of words is the harder it gets to crack/guess the seed.
A 12 word phrase or so I am sure I can always remember, 20 might be a bit much.
A 24 word seed phrase has about the same
security as the private key of bitcoins itself.
Means that with any seed longer than 24 words its 'more profitable' to 'attack' the private key instead. Please note that we are talking about more than 10
77 possibilities.
A 12 word seed gives you about 5 * 10
39 different seeds. Thats clearly smaller but still high enough to be considered non-crackable (currently).
Also is this possible to do with Monero ?
Theoretically this works with every currency. It just has to be implemented.