Keytab file created and used by Kerberos, a network authentication protocol; contains pairs of Kerberos principals along with an encrypted copy of that principal's key.

The KEYTAB file is used to authenticate a principal on a host to Kerberos without any user interaction or having to store a password in a plain text file. The file is encrypted but should be secured well because whoever has access to the file can act as that principal. Kerberos provides authentication tools and secret-key cryptography to secure communications by client/server applications. The Massachusetts Institute of Technology (MIT) has made a free implementation of the protocol available in source form. The protocol is also available in a variety of commercial products.