python-mnemonic VS OSTN02c

... and BIP-39

Look-up "BIP32", "BIP39" and "BIP44", those will point you to documents describing precisely how seed phrases are converted into crypto keys.

i think bip39 is what you want to look up.

An HD wallet that follows the BIP-39 standard generates its 512-bit master extended key from a seed based on 128, 160, 192, 224 or 256 bits of entropy, which it encodes as a mnemonic for ease of use by human users, and an optional passphrase (additional entropy). The master extended key for a BIP-32 HD wallet is always 512 bits, and the private keys in the key tree are always 32 bytes (256 bits), but adding a passphrase increases the entropy of the seed used to calculate the 512-bit master extended key.

Checkout the bip https://github.com/bitcoin/bips/blob/master/bip-0039.mediawiki and this code https://github.com/trezor/python-mnemonic

The 18 words is in the standard, but I don't know how widely it's actually implemented. Trezor definitely has an 18-word recovery option though. I'd use the reference implementation to verify that the seed is legit, then you can go from there.

Throughout all these different wallets, we are still dealing with really long strings of letters and numbers that are difficult for humans to retain and process. Then comes along BIP-39, a proposal which offers as a solution a way to convert those long strings of binary or hexadecimal digits into something that is much easier for humans to read and transport. This is the most popular implementation for private keys and most of you have probably already interacted with it.

New seed phrases are typically 12-24 randomly generated words, not user provided... and when you need to "change a password" in a crypto wallet, you can generate a new private key and move funds.

Check out BIP-39 [0] for more details.

[0] - https://github.com/bitcoin/bips/blob/master/bip-0039.mediawi...