What two conditions must a digital signature meet?

• A. It must be unforgeable and authentic.
• B. It must be easily forgeable and hidden
• C. It must be encrypted with a private key only
• D. It must be symmetric and ephemeral

Answer: (A)

A digital signature must be unforgeable and authentic. It’s created with the signer’s private key, and anyone can verify it using the signer’s public key. Unforgeable means someone without the private key can’t forge a valid signature on arbitrary data, protecting against impersonation. Authentic means, once verified, you’re confident about who signed the message and that the content hasn’t been altered, because the signature proves the signer possessed the corresponding private key. This also gives non-repudiation—the signer can’t credibly deny having signed it. The other statements misunderstand how signing works: signatures aren’t simply “encrypted with a private key,” and they’re not about being easily forgeable or about symmetric/ephemeral properties.