What is correct about digital signatures?

A digital signature is created by hashing the document and encrypting that hash with the sender’s private key. Since the hash is specific to the original content, any change to the document invalidates the signature, making it non-transferable to another document.

Reference – CEH v13 Official Study Guide:

Module 20: Cryptography

Quote:

“Digital signatures are based on hashing the document and signing the digest with the private key. This makes each signature unique to the document and ensures tamper resistance.”

Incorrect Options:

B. Incorrect — signature is tied to one document.

C. Hashes are not plain; they are encrypted.

D. Keys can be reused, but signatures are document-specific.