Which of the following is the best way to securely store an encryption key for a data set in a manner that allows multiple entities to access the key when needed?

Public key infrastructure (PKI) is a framework that uses public and private keys for secure communication and authentication. While PKI is essential for managing digital certificates and encrypting data, it does not inherently provide a secure method for storing a single encryption key that multiple entities can access on demand. Instead, it focuses on the exchange of keys rather than centralized key storage.

An open public ledger, like those used in blockchain technology, records transactions transparently and securely. However, it is not designed for the secure storage of encryption keys. An open ledger may expose sensitive information and does not facilitate controlled access for multiple entities, making it an unsuitable choice for key management.

Public key encryption involves the use of a pair of keys (public and private) to secure data transmission. While it provides a robust encryption method, it does not address the need for centralized key storage accessible by multiple entities. Each entity would manage its own keys, which complicates the scenario of shared access.