Ира, это не может быть и то, и другое. Для "не разглашайте свой пароль" есть стандартное выражение - disclose password.

Shared password - это именно "общий, совместный" - для коллективного пользования.

If a shared password is required to enter the Forum (ie all the Participants use the same password) you will be asked to enter that password and then type a ...
site.www.umb.edu/Help/Session_Registration.html

Allotting separate passwords to each user of a system is usually preferable to having a single password shared by legitimate users of the system. This is partly because people are more willing to tell another person (who may not be authorized) a shared password than one exclusively for their use. Single passwords are also much less convenient to change because many people need to be told at the same time, and they make removal of a particular user's access more difficult. Per-user passwords are also essential if users are to be held accountable for their activities, such as making financial transactions or viewing medical records.

http://www.answers.com/topic/password