Using PQHD

PQHD (Post-Quantum Hierarchical Deterministic) is Tidecoin Core’s wallet key derivation system. Unlike BIP-32, it is hardened-only and works across all five PQ signature schemes. You can run multiple seeds in one wallet and set a per-seed scheme policy for receive and change addresses.

This page is for wallet operation. The canonical derivation specification lives at Protocol / PQHD.

Why PQHD exists

Bitcoin-style BIP32 relies on elliptic-curve public derivation and xpubs. Tidecoin uses post-quantum lattice signatures, so PQHD uses hardened-only hash-based derivation instead. That means derivation metadata can describe the path, but secret seed material remains wallet-local.

Path shape

PQHD paths follow:


m / purpose' / coin_type' / scheme' / account' / change' / index'

The fixed values are:

Field	Value
`purpose'`	`10007'`
`coin_type'`	`6868'`
`scheme'`	Tidecoin PQ scheme prefix
`change'`	`0'` for receive, `1'` for change

All elements are hardened.

Scheme prefixes

Scheme	Prefix
Falcon-512	7
Falcon-1024	8
ML-DSA-44	9
ML-DSA-65	10
ML-DSA-87	11

Mainnet currently allows Falcon-512 before AuxPoW. Additional schemes are implemented but gated by AuxPoW activation on mainnet. See Activation Status.

Wallet RPCs

RPC	Purpose
`setpqhdpolicy`	Set default receive and change schemes.
`listpqhdseeds`	List seed IDs and default receive/change markers.
`importpqhdseed`	Import a 32-byte PQHD master seed in hex form.
`setpqhdseed`	Select default receive and change seed IDs.
`removepqhdseed`	Remove an unused seed that is not a default.

Example policy command:


tidecoin-cli -rpcwallet="<wallet>" setpqhdpolicy "falcon-512" "falcon-512"

Example seed listing:


tidecoin-cli -rpcwallet="<wallet>" listpqhdseeds

Descriptors and PSBT

Tidecoin descriptor wallets use pqhd(...) expressions, for example:


wpkh(pqhd(<seedid32>)/10007h/6868h/7h/0h/0h/*h)

PSBT can carry Tidecoin proprietary PQHD origin metadata under the tidecoin identifier. Wallet RPCs expose include_pqhd_origins options where this metadata is useful for offline signing workflows.

Backup warning

PQHD seeds are secret wallet material. A descriptor string records derivation intent; it is not a replacement for a wallet backup or seed backup.