Moving Bitcoin's payment layer to Lightning Network doesn't undermine base layer security—in fact, it enhances overall network resilience by offloading small, frequent transactions from the congested main chain.
Lightning operates as a second-layer protocol using bidirectional payment channels secured by on-chain smart contracts (via HTLCs). Users lock BTC in multisig channels on the base layer, then route off-chain payments instantly and cheaply. Security relies on Bitcoin's core features: time-locked scripts (e.g., CheckSequenceVerify) penalize fraud via "justice transactions," forcing honest behavior or loss of funds. If disputes arise, channels close on-chain, settling via Bitcoin's proof-of-work consensus.
Key contrasts to concerns: No central points of failure; channels inherit base layer security. However, users must manage private keys carefully—channel breaches could lead to force-closures. As of 2025, Lightning handles millions in daily volume (e.g., via nodes like those from Jack Dorsey's integrations), reducing base layer spam and preserving its focus on high-value settlements. For deeper dives, see Lightning's original whitepaper or recent analyses on Wikipedia.