What does Derrick need from the sender to validate a digitally signed message sent with asymmetric encryption?

To validate a digitally signed message sent with asymmetric encryption, Derrick needs the sender's public key. In asymmetric encryption, a pair of keys is used: a private key that is kept secret by the sender and a public key that is shared with anyone who needs to verify the sender's signatures.

When a message is signed, the sender uses their private key to create the digital signature, which is unique to both the message and the key used to sign it. Anyone receiving the signed message can then use the sender's public key to verify the signature. This verification process ensures that the message has not been altered and confirms the identity of the sender, as only the sender's private key could have created the signature associated with the message.

Without the sender's public key, Derrick would not be able to perform this verification process. Other pieces of information mentioned, such as the sender's private key, the original plaintext message, or an encryption password, are not required for validating the signature on the message. The process relies solely on the public key for verification against the signature created with the private key.