How Does a Proof-of-Stake (PoS) System Deter a 51% Attack?
A PoS system deters a 51% attack by making it prohibitively expensive to acquire 51% of the total staked cryptocurrency (the native token). If an attacker successfully gains 51% of the stake and attempts to create a malicious chain, the protocol's "slashing" mechanism will detect the double-signing and automatically destroy (slash) the attacker's staked funds.
This guaranteed, permanent loss of capital makes the attack economically irrational, as the attacker's investment would be immediately and significantly devalued.
Glossar
Staked Cryptocurrency
Yield ⎊ Staked cryptocurrency represents a capital deployment strategy wherein digital assets are actively held within a validation mechanism, typically Proof-of-Stake blockchains, to support network operations and, in return, generate additional cryptocurrency as reward.
PoS System
Architecture ⎊ This consensus mechanism relies on a set of validators who lock up a quantity of the native cryptocurrency as collateral to gain the right to propose and attest to new blocks on the chain.