The Identity Documents Act was amended declaring the provider of certification services a vital service provider:
(31) The provider of certification service that enables digital identification and digital signing with the certificate which is entered in the documents issued on the basis of this Act is the provider of vital service specified in clause 36 (1) 8) of the Emergency Act.
[RT I, 03.03.2017, 1 – entry into force 01.07.2017]
In practice, at least currently the new status does not introduce significant new requirements, since for SK as a qualified trust service provider the operational requirements set by law were quite high anyway.
Links:
https://www.riigiteataja.ee/en/eli/521062017003/consolide
https://geenius.ee/uudis/riik-hakkab-voimaliku-id-kriisi-jaoks-kirjutama-viimsepaeva-protokolli/
“The Ministry of Economic Affairs and Communications is compiling a working group whose task is to write a “late-day protocol”, a regulation that clearly states how long, for example, ID-card or digital signing services can be down and how and in what order they should be restored.”