We would like to add digital signatures to the course accomplishment certificates
that would allow someone who knows KU,CA, the public key of our certificate authority,
to validate that a certificate was generated by Udacity and earned by the person
whose name is in the certificate.
Assume m is the certificate string.
For example, "Certificate of accomplishment with highest distinction earned
by Alice Hacker in CS587."
Assume E is a strong public key encryption algorithm,
H is a cryptographic hash function, and r si a random nonce.
Which of these schemes would allow Udacity to generate unforgable,
verifiable, signed certificates.
Check all that are valid.
