You cannot use "1", "b", "i" and "o". *
But if I'm not wrong Rana stops you upfront if you try an incompatible prefix.
How long is it?
*Reference: https://en.bitcoin.it/wiki/BIP_0173
It doesn't use invalid characters. But I'm not fluent in bech32m encoding, so maybe some character sequences just don't happen and therefore I can't find them?
It's 5 prefix + 3 suffix. I did a 4 + 4 a while back and that took about 3 days, but maybe I was extremely lucky then.
Extremely lucky! 8 chars in 3 day is a no way with a consumer hardware. 6 chars requires 2-5 hours, 7 many days, I suppose 8 is about weeks.
Said that, the last 6 chars are a checksum, so inuitivelely it is possible that if you personalize them this can heavily (exponentially?) increase the matching complexity.
Don't remember if nostr:npub12rv5lskctqxxs2c8rf2zlzc7xx3qpvzs3w4etgemauy9thegr43sf485vg did some experiments on this, maybe he can help.
