Expiry

Full Title or Meme

Certificates and Credentials typically include an Expiry date-time or event, such as "on first use".

Context

• Many digital documents include a start data and an Expiry date.
• Many digital documents include a nonce or serial number which typically is used to ensure that the document is only processed on time, and then expires.

Problems

Expiry can be devilishly difficult to determine.

• Typically, a Certificate will expire on a give data and time, which seems very clear.
• When a key with a certificate is used to sign a document, should the data of validation or the date of signing be operative?