In access control, data that authenticates the identity of a client or a service and, together with a temporary encryption key (a session key), forms a credential.
Adapted from: IETF RFC 4120 Kerberos V5, July 2005; Conrad, E., Misenauer, S., & Feldman, J. (2010). CISSP® Study Guide. Burlington, MA: Syngress.
Source: NICCS™ Portal Cybersecurity Lexicon, National Initiative for Cybersecurity Careers and Studies (https://niccs.us-cert.gov/glossary) as of 11 November 2015, Global Standards