For most PGP use, the MDC only serves as an integrity check [1]. That is the same for the proposed modes as well. In the case of symmetrical encryption it does

For most PGP use, the MDC only serves as an integrity check [1]. That is the same for the proposed modes as well. In the case of symmetrical encryption it does in fact serve to authenticate the encrypted material based on the passphrase. It does not use the popular combination of an encryption function acting more or less independently of a MAC (message authentication code). It uses a different method[2]. This seems to cause much confusion. [1] https://articles.59.ca/doku.php?id=pgpfan:authenticated https://articles.59.ca/doku.php?id=pgpfan:authenticated [2] https://articles.59.ca/doku.php?id=pgpfan:mdc https://articles.59.ca/doku.php?id=pgpfan:mdc