What Is the Cryptographic Mechanism That Protects a User’s Wallet from a 51% Attack?

A user's wallet is protected by public-key cryptography, specifically the use of a private key to digitally sign transactions. A 51% attacker only controls the ability to confirm or reverse blocks, not the private keys required to authorize spending from a wallet.

The attacker cannot generate a valid signature for a transaction from a wallet they do not own, making coin theft impossible.