I wonder if you string together enough words can it be a valid key?

I would hope so, sentences and words are some of the most secure passwords/phrases you can use

Words are the least secure way to generate a password of a given length because you are limiting your character set to 26, and character N gives you information about the character at position N+1

The most secure way to generate a password is to uniformly pick bytes from the entire character set using a suitable form of entropy

That’s only really true if you’re going to be storing the password in a secure vault after randomly generating it; otherwise, it’s terrible because 1) nobody will be able to remember it so they’ll be writing it down, and 2) it’ll be such a pain to type that people will find ways to circumvent it at every possible turn

Pass phrases, even when taken with the idea that it’s a limited character set that follows a semi predictable flow, if you look at it in terms of the number of words possible it actually is decently secure, especially if the words used are random and not meaningful to the user. Even limiting yourself to the 1000 most common words in the English language and using 4 words, that’s one trillion possible combinations without even accounting for modifying capitalisation, adding a symbol or three, including a short number at the end…

And even with that base set, even if a computer could theoretically try all trillion possibilities quickly, it’ll make a ton of noise, get throttled, and likely lock the account out long before it has a chance to try even the tiniest fraction of them

Your way is theoretically more secure, but practically only works for machines or with secure password storage. If it’s something a human needs to remember and type themselves, phrases of random words is much more viable and much more likely to be used in a secure fashion.

Generally people don’t memorize private keys, but this is applicable when generating pass phrases to protect private keys that are stored locally.

Leaving this here in case anyone wants to use this method: www.eff.org/dice