Most large losses come from compromised signing processes and people, not from broken cryptography. The main risk categories are: Key theft: malware, cloud misconfiguration, insider access, or weak MPC share separation. Signing-interface compromise: attackers change what signers see, so approvers sign a malicious transaction they believe is routine. Phishing and approval scams: users sign token approvals or permits that let drainer contracts empty the wallet. Address poisoning: attackers send tiny transfers from look-alike addresses so users copy the wrong one from history. Smart contract bugs in smart accounts, bridges or DeFi protocols the wallet connects to. Supply chain attacks through compromised libraries, SDKs or browser extensions. Operational errors: wrong network, wrong address, lost backups. A cryptocurrency wallet development solution should address each of these explicitly in its threat model.