What method can be used to guarantee that a document originates from you and no one else?

Question

Exhibit

Options

• Apublic key encryption, encrypting the document with the private key and making the public key available to others
• Bsymmetric encryption, encrypting the document with the public key and making the different private key available to others
• Csymmetric encryption, encrypting the document with the secret key and making the same secret key available to others
• Dpublic key encryption, encrypting the document with the private key and making the private key available to others

• A
  79% (30)
• B
  3% (1)
• C
  8% (3)
• D
  11% (4)

Explanation

Option A is correct because encrypting with your private key - which only you possess - creates a digital signature. Anyone can use your publicly available public key to decrypt and verify the document, and since only your private key could have produced that result, the origin is mathematically guaranteed to be you.

B is wrong on two counts: "symmetric encryption" by definition uses the same key for both parties, so pairing it with a public/private key pair is a contradiction - that describes asymmetric (public key) encryption.

C is wrong because sharing the secret key with others means anyone holding it could have encrypted the document, destroying any proof of origin - symmetric encryption cannot authenticate a single sender.

D is wrong for an obvious but critical reason: sharing your private key with others means they can impersonate you, completely defeating the purpose of proving the document is uniquely yours.

Memory tip: Think of your private key as your handwritten signature - only you can produce it, but anyone can visually verify it using your publicly known signature (public key). "Private key signs, public key verifies."

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