From RFC 2585

application/pkix-crl

   To: ietf-types@iana.org
   Subject: Registration of MIME media type application/pkix-crl

   MIME media type name: application

   MIME subtype name: pkix-crl

   Required parameters: None

   Optional parameters: version (default value is "1")

   Encoding considerations: will be none for 8-bit transports and most
   likely Base64 for SMTP or other 7-bit transports

   Security considerations: Carries a cryptographic certificate
   revocation list

   Interoperability considerations: None

   Published specification: draft-ietf-pkix-ipki-part1

   Applications which use this media type: Any MIME-complaint transport

   Additional information:
     Magic number(s): None
     File extension(s): .CRL
     Macintosh File Type Code(s): none

   Person & email address to contact for further information:
   Russ Housley <housley@spyrus.com>

   Intended usage: COMMON

   Author/Change controller:
   Russ Housley <housley@spyrus.com>