According to some guy on reddit you are correct: https://www.reddit.com/r/crypto/comments/3et3va/why_does_totp_use_a_shared_secret_instead_of_an/cti7l7b https:/

According to some guy on reddit you are correct: https://www.reddit.com/r/crypto/comments/3et3va/why_does_totp_use_a_shared_secret_instead_of_an/cti7l7b https://www.reddit.com/r/crypto/comments/3et3va/why_does_tot... The post also gives a justification for using symmetric encryption, it lets the tokens users enter be shorter.