Support Bip32 HD for solana keypair files

[CriesofCarrots]

Problem

Right now, a solana keypair file generated from a particular bip39 seedphrase is a "raw" ed25519 keypair; it does not use the same hashing mechanism from entropy as bip32 master-key derivation does, and does not produce/preserve the chain code that is needed bip32 and bip44 hierarchical derivation.

Proposed Solution

Extend solana key files to contain additional data, including the chain code or perhaps even the raw entropy. This would enable solana command-line tools to support bip32 HD from solana-keygen key files, following #5246

[CriesofCarrots]

cc @t-nelson

[CriesofCarrots]

Data to store in keyfile:

• seedphrase/entropy
• version
• type, cleartext vs (down-the-road) encrypted
• base key for verification (either bip32 master key, or solana bip44 base)
• library of derived pubkeys

[dahifi]

Is this why we can't import seed phrases derived from Sollet or similar into the solana-keygen recover?

[CriesofCarrots]

@dahifi , no, you actually can use seed phrases with solana-keygen recover using prompt: or ASK as the keypair parameter:

$ solana-keygen recover -h
solana-keygen-recover
Recover keypair from seed phrase and optional BIP39 passphrase
...
ARGS:
    <KEYPAIR>    `prompt:` URI scheme or `ASK` keyword

See https://docs.solana.com/wallet-guide/paper-wallet#hierarchical-derivation

[CriesofCarrots]

This still seems like a potentially useful idea, but is on no one's any-term radar. I'm going to close for now, but we know where to find this again if we want to pick it up in the future.