What is Zero-Knowledge Scalable Transparent Argument of Knowledge (zk-STARK)?

A zero-knowledge "scalable" transparent argument of knowledge (zk-STARK) is a specialized type of cryptographic proof that is used to ensure privacy on blockchain-based distributed ledger systems. It works by proving that one party is in possession of specific data without actually revealing the data to the network. Zk-STARKs are a crucial element of Zero-Knowledge Rollups (zk-Rollups), a popular Layer-2 scaling solution. Zk-STARKs are a new development based on zero-knowledge succinct non-interactive arguments of knowledge (zk-SNARKS), and are distinguished by being more trustless than their predecessor.