A custody stack is the full set of systems, policies, and controls that protect digital assets while they are stored and moved. It includes wallets, key management, signing workflows, withdrawal approval rules, access control, monitoring, and recovery procedures. In crypto and other asset platforms, the custody stack is the practical boundary between safe funds and funds that can be spent immediately.
This matters because attackers rarely need to “break the blockchain” itself; they often target the custody stack around it. If signing keys, approval steps, or admin accounts are exposed, an attacker can authorize valid transfers that are hard or impossible to reverse. Defenders harden the custody stack with key separation, multi-approval policies, spending limits, address allowlists, offline reserves, and anomaly detection. A weak custody stack can turn a small compromise into a large asset drain.