A computer-implemented method comprises sending, to a first device, a request for a signed certificate, the request for the signed certificate comprising a signed hash of data associated with a user, a corresponding public key of the user, and the data associated with the user; sending, to a second device different from the first device, a request for the signed certificate, the request comprising information to retrieve the signed certificate; and obtaining, from the second device, a signed certificate, the signed certificate comprising the public key of the user, the hash of the data associated with the user, and information indicating a health status of the user, the data associated with the user being absent from the signed certificate.