Expiry

[dirkx]

We currently say:

• The Expiration Time MUST not exceed the validity time in the DSC. The verifier SHOULD check this.

We have the worry that MS get this wrong in the tail of the pandemic - and continue issuing right up to the end of the DSC validity.

We can forego all dates in the DSC -- and only look at 'esp' in claim 4.

We could change this to

• The Expiration Time MAY exceed the validity time in the DSC. The verifier MUST therefore not check this; and ignore any and all DSC Key usage and validity data.

But this has the risk that implementors get it wrong ? So this is about an ops/governance mistake v.s. a implementor mistake.

[dirkx]

Given the rush - I would suggest we say:

• DSCs SHOULD be valid for at least 2 years.
• MS should renew their DSCs at least annually
• The Secretariat/Working group will actively encourage MS to renew and revisit their DSC if the freshest DSC is known that has less than than typical (max) vaccination coverage.

[fredriklj]

I think it is important to state exactly what validation rules must be implemented by the verifier. In this we currently say that all keys in the trusted list may be used, but that key usage may have to be verified. And keep this separate from the key management practices put in place by the issuer of the CSCA/DSC certificates.

An issuer of HCERTs could have a key management practice in place where a new key is introduced for. for example, each quarter, and used to issue HCERT's with a validity period of 3 months. Which means a signing key can be withdrawn 6 months after it has been introduced (3 months after its operational period has ended). This type of key management scheme would make sense if an issuer is not able to use an HSM.

Regardless it seems dangerous to try to indicate what key management practices are in place by using Not valid before/Not valid after in the X.509 certificate. And key management practices may change down the road. But yes, we should give some kind of recommendation on reasonable timings and considerations tied to this that must be made by each issuer.

[jschlyter]

I agree with @fredriklj - once a key published on the trusted list, verifiers should be allowed to use it to verify signatures. If the trusted list issuer don't want verifiers to use a key, don't put it on the list.

[dirkx]

Can you folks Merge and Close this one if you feel this is now well enough described ?

[fredriklj]

I think this was address in the merging of PR #16 .