2005-12-20 2006-09-27 0x0000-0x00FF Standards Action 0xFF00-0xFFFF Standards Action 0x0100-0xFEFF IETF Review based on RFC documentation of the certificate type 0 Reserved 1 PKIX X.509 as per PKIX 2 SPKI SPKI certificate 3 PGP OpenPGP packet 4 IPKIX The URL of an X.509 data object 5 ISPKI The URL of an SPKI certificate 6 IPGP The URL of an OpenPGP packet 7 ACPKIX Attribute Certificate 8 IACPKIX The URL of an Attribute Certificate 9-252 Unassigned 253 URI URI private 254 OID OID private 255 Reserved 256-65279 Unassigned 65280-65534 Experimental 65535 Reserved