Which key does a sender use to create a digital signature?

### Why this is right The private key is the signing key in the workflow. A recipient can use the matching public key to check the resulting signature. ### The concept A digital signature is a cryptographic value associated with a document. The signing process uses the sender’s private key and a hash, a compact value calculated from the document’s contents. Verification checks whether the signature is consistent with the document and the corresponding public key. Signing does not encrypt the document, so its contents remain readable unless a separate encryption step is used. ### The other options - **B. The recipient's public key**: used to verify in this workflow, not to create the sender’s signature. - **C. A shared symmetric key**: used in symmetric-key operations, not the described public-key signature process. - **D. The recipient's private key**: belongs to the recipient and is not the sender’s signing key. ### Terms - **Digital signature**: A cryptographic value used to check who signed data and whether it changed. - **Private key**: A secret key held by its owner. - **Public key**: A key that can be shared and used to verify a signature. - **Hash**: A compact value calculated from data. ### Remember The sender signs with a private key; the recipient verifies with the matching public key.