Answer:
To create a public key signature, you would use the _private_ key.
Explanation:
To create a public key signature, a private key is essential to enable authorization.
A private key uses one key to make data unreadable by intruders and for the data to be accessed the same key would be needed to do so.
The login details and some important credentials to access user data contains both the user's public key data and private key data. Both private key and public key are two keys that work together to accomplish security goals.
The public key uses different keys to make data readable and unreadable.
The public key is important to verify authorization to access encrypted data by making sure the access authorization came from someone who has the private key. In other words, it's a system put in place to cross-check the holder of the private key by providing the public key of the encrypted data that needed to be accessed. Though, it depends on the key used to encrypt the data as data encrypted with a public key would require a private key for the data to be readable.