Effective 1 December 2014, digital ID and e-Residency digital ID card certificates are issued using the SHA-256 hash algorithm. The issuance of certificates for the ID card, residence permit card and Mobile ID using the SHA-256 hash algorithm began on 1 January 2015.
From the start of 2015, all certificates issued upon renewal of certificates also use the SHA-256 hash algorithm. The organisation certificates issued by SK use the SHA-256 hash algorithm by default already since the summer of 2014
The reason for the change is that the security of the SHA-1 hash algorithm used until now will weaken in the coming years. You can find out more about research on the areas of use and lifecycle of cryptographic algorithms here
The new version of the digital certificate profile of Estonian personal identity documents is available here