Master Extended Key

The master extended key is the top-level key in a hierarchical deterministic wallet structure that can be used to derive all subsequent keys in the tree. It consists of both a private key and a chain code, which together allow for the generation of child keys.

If an extended public key is shared, it allows others to derive all child public keys, which is useful for accounting and monitoring incoming transactions without granting the ability to spend funds. However, the master private extended key is extremely sensitive, as its compromise allows an attacker to derive all private keys in the wallet.

Protecting the master extended key is a paramount concern for institutional custody and multi-signature setups. It represents the central root of trust for an entire wallet portfolio.