Dorian Is sending a digitally signed email to Polly, with which key is Dorian signing this message and how is Poly validating It?

Digital signatures use asymmetric cryptography to provide authenticity, non-repudiation, and integrity. The sender (Dorian) creates a signature by using their own private key to encrypt a hash of the message. This ensures that only Dorian could have created it. The recipient (Polly) then uses Dorian's corresponding public key to decrypt the signature and verify that the message hash matches. This process confirms the sender's identity and that the message was not altered in transit.

A. Signing is done with a private key, and verification with a public key. This option reverses the process, which is functionally incorrect.
B. Signing with the recipient's (Polly's) public key is for encrypting the message for confidentiality, not for creating a digital signature.
D. The sender (Dorian) would not have access to the recipient's (Polly's) private key, as private keys must always remain secret.

1. National Institute of Standards and Technology (NIST). (2013). FIPS PUB 186-4: Digital Signature Standard (DSS). Section 4, "Digital Signature Generation and Verification."

2. Katz, J., & Lindell, Y. (2014). Introduction to Modern Cryptography (2nd ed.). CRC Press. Chapter 12, "Digital Signatures," provides a formal definition and security model for digital signatures.

3. Pfleeger, C. P., Pfleeger, S. L., & Margulies, J. (2015). Security in Computing (5th ed.). Prentice Hall. Chapter 2.3, "Public Key Cryptography," explains the use of private keys for signing and public keys for verification.