Public keys are used for which of the following?

Wireless messages are decrypted using shared or session keys in symmetric encryption, not with a recipient's public key.

When a sender creates a digital signature, they hash the message and encrypt that hash with their private key. The recipient uses the sender's public key to decrypt (verify) that encrypted hash, confirming the signature's authenticity and that the message has not been altered. This is the primary cryptographic use of a public key in signature verification.

Bulk encryption of email traffic uses symmetric algorithms (such as AES) for performance reasons; public keys are used only to exchange or protect the symmetric key.

Web browser traffic (HTTPS/TLS) uses the server's public key during the handshake to establish a session key, but the bulk traffic encryption itself uses symmetric keys, not the public key directly.