http://www.rfc-editor.org/rfc/rfc3445.txt
RFC 3445: Limiting the Scope of the KEY Resource Record (RR), D. Massey, S. Rose2002-12-01T23:00:00-00:00This document limits the Domain Name System (DNS) KEY Resource Record (RR) to only keys used by the Domain Name System Security Extensions (DNSSEC). The original KEY RR used sub-typing to store both DNSSEC keys and arbitrary application keys. Storing both DNSSEC and application keys with the same record type is a mistake. This document removes application keys from the KEY record by redefining the Protocol Octet field in the KEY RR Data. As a result of removing application keys, all but one of the flags in the KEY record become unnecessary and are redefined. Three existing application key sub-types are changed to reserved, but the format of the KEY record is not changed. This document updates RFC 2535. [STANDARDS-TRACK]