Patent ID: 9548970
Date: 2017-01-17
CPC Classifications: G06F,H04L

Claim:
1. A method for managing unlinkable database user identifiers, the method comprising: distributing to a first database a first encrypted user identifier, a first database identifier, and a first database user identifier; distributing to a second database a second encrypted user identifier, a second database identifier, and a second database user identifier; receiving from the first database a third encryption and a fourth encryption, the third encryption being formed from the first encrypted user identifier, the second database identifier, and a message comprised in the fourth encryption; decrypting the third encryption thereby obtaining a decrypted value; deriving a blinded user identifier from the decrypted value; sending an encrypted blinded user identifier and a fourth encrypted value to a second server thereby enabling the second server to compute the second database user identifier from an encrypted blinded database user identifier and a decrypted fourth encrypted value; generating a blinded encrypted expression comprising the first database identifier after receiving the first encrypted user identifier; and distributing the first database identifier in a blinded, encrypted form using thereby the first encrypted user identifier, wherein the second encrypted user identifier is generated using an encryption function using a public key of a central authority and a user identity as input and wherein the second database user identifier is generated using a pseudo random function using as input a user identity and the second database identifier, wherein the first encrypted user identifier, the second encrypted user identifier, the first database user identifier and the second database user identifier are deleted after the distribution to the first database and the distribution to the second database, respectively.