Validity of signatures

A signature is valid if it was generated during the validity period of the corresponding pub key certificate.

• The validity period starts on the certificate’s NotBefore date field.

• By default, the validity ends on the NotAfter date field.

  • Unless revoked.

A private key can be used out of that period.

• But the signature it produces is invalid.

A public key certificate can be used anytime.

• Namely, after the validity period to check past signatures.