For what purpose?
There are no special privileges for anyone, not even Congressmen and cabinet members, except that Congressmen are exempt from arrest when traveling to and from Congress, and cannot be sued for statements made in chamber during deliberations.
Kerry is illegally withholding access to witnesses from Congress. He has no "secretary-source privilege."
Why should a journalist?
-PJ
There's an attorney-client privilege, doctor-patient privilege, spousal privilege, and and priest-penitent privilege. All of those privileges allow (and in many cases require) witnesses to withhold information depending on the source of the information. I don't think such a privilege ought to be extended to journalists, but it would not be unprecedented.