Which of the following BEST ensures the integrity of transactions to intended recipients?

PKI uses a hierarchy of Certificate Authorities (CAs) to issue digital certificates that bind public keys to verified identities, ensuring that transactions are encrypted for and authenticated by the intended recipient. Digital signatures generated via PKI provide both integrity verification (detecting tampering) and non-repudiation, confirming the transaction originated from the claimed sender. This makes PKI the most comprehensive and widely adopted solution for ensuring transaction integrity to intended recipients.

Blockchain technology ensures immutability and distributed record-keeping but is primarily a ledger/consensus mechanism rather than a direct cryptographic framework for verifying the identity of specific intended recipients in general transactions.

Pre-shared keys (PSK) rely on a symmetric secret shared between parties in advance, which does not scale well and lacks the certificate-based identity verification needed to confirm transactions are reaching the intended recipient.

Web of trust is a decentralized model used in PGP where users vouch for each other's keys, but it lacks the structured, hierarchical authority and broad interoperability of PKI, making it less reliable for ensuring integrity to intended recipients at scale.