Abstract: An apparatus is provided for verifying a plurality of cryptographically signed user electronic records using a corresponding cryptographic proof. Cryptographic keys for verifying the plurality of user electronic records, and corresponding user electronic record schemas are cached in a local data store. The apparatus obtains up-to-date copies of the cryptographic keys and schemas for caching from a remote data store when the remote data store is accessible by the apparatus over the internet. Upon receipt of the data from the user device, when the remote data store is not accessible, the apparatus is configured to identify the cached cryptographic key and schema corresponding to the received cryptographically signed electronic record and cryptographic proof; and determine a verification result for the cryptographically signed electronic record based on the cryptographic proof and the identified cached cryptographic key and schema. An indication of the verification result is then output from the apparatus.