What type of key is used to decrypt data that was encrypted with a public key?

When data is encrypted using a public key, it is designed to ensure that only the corresponding private key can decrypt the information. In asymmetric cryptography, which utilizes public and private key pairs, the public key is made available to anyone who wishes to send encrypted data, while the private key is kept secret by the recipient.

This design provides a crucial layer of security, as it allows individuals to communicate confidentially without needing to share a secret key beforehand. Hence, only the holder of the private key can decrypt messages that have been encrypted with the associated public key.

The other options refer to different types of encryption methods or keys. Shared keys pertain to symmetric encryption, where a single key is used for both encryption and decryption. Public keys and symmetric keys, while potentially relevant in their contexts, do not perform the decryption of data encrypted with a public key. Thus, the private key is the necessary component for this type of decryption scenario.