OptionalValidity vs. PrivateKeyUsagePeriod / Explicit vs. Implicit Tagged Obejects

[jweu]

.../asn1/crmf/OptionalValidity from RFC4211 Appendix B is listed inside DEFINITIONS IMPLICIT TAGS ... END
and
.../asn1/x509/PrivateKeyUsagePeriod from RFC 5280 Appendix A.2 is listed inside DEFINITIONS IMPLICIT TAGS ... END

Why is OptionalValidity explicitly tagged and PrivateKeyUsagePeriod is implicitly tagged. Is this correct ? These implementations are throwing an exception while parsing if the tagging is not the expected one.

Why is the explicit tagged value of a PrivateKeyUsagePeriod not always silently accepted as an alternative ?

[peterdettman]

The fields of OptionalValidity are of type Time, which is a CHOICE type:

OptionalValidity ::= SEQUENCE {
    notBefore [0] Time OPTIONAL,
    notAfter [1] Time OPTIONAL } --at least one must be present

Time ::= CHOICE {
    utcTime UTCTime,
    generalTime GeneralizedTime }

Implicit tagging cannot be used with an (untagged) CHOICE type, per X.680 30.6/30.8, despite the module IMPLICIT (or AUTOMATIC) TAGS. Therefore explicit tagging is used. PrivateKeyUsagePeriod's fields are GeneralizedTime, which is not a CHOICE type, so the module IMPLICIT TAGS applies there.

[jweu]

Thank you very much. Please add the definition of "Time" to the comment at OptionalValidity.java.

[peterdettman]

I've updated comments to make it clearer that a CHOICE is involved.