ITPEC FE Morning April 2022 Question 38

Key generation algorithm — it is the one algorithm of a public-key scheme that produces the matching private and public keys.

A digital signature scheme, on which PKI builds, consists of three algorithms:

• •Key generation outputs a key pair, for example RSA chooses two large primes and derives both keys from them.
• •Signing uses the private key to produce a signature on a message, usually on its hash value.
• •Verification uses the public key to check that signature.

PKI then binds the public key to its owner with a certificate issued by a certificate authority.

Answer (b)

Why not others:

• •(a) Hashing algorithm — produces a fixed-length digest of a message and uses no key at all.
• •(c) Signature verification algorithm — takes an existing public key, the message and the signature, and reports whether the signature is valid.
• •(d) Signing algorithm — takes an existing private key to produce a signature.

Key rule: Key generation creates the key pair, signing uses the private key and verification uses the public key; a hash function uses no key.

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