Is it permissible to reveal a secret after its owner has disclosed it publicly, even though I swore to keep it?

Whoever is entrusted with a secret is not permitted to reveal it. However, if the owner of the secret reveals his secret to the public, then there is no harm upon the one who was entrusted with the secret in mentioning it, and he is not considered to have broken his trust thereby, because the owner of the secret himself disclosed it. Nevertheless, it is preferable not to mention it unless there is an overriding benefit in doing so.