CRYPTOGRAPHICALLY SECURE DATA PROTECTION

This disclosure relates to data security and cryptography. In one aspect, a method includes receiving a request for a subscription token for a given user by a data security system from a publisher computing system of a publisher. The request includes user identification information provided to the publisher by the given user when subscribing to electronic content of the publisher. The data security system generates the subscription token which includes a set of data that includes a first encrypted user identifier generated by encrypting a first user identifier for the given user using an encryption key of the data security system, and, for each of one or more content platforms, an attachment element that includes a second encrypted user identifier generated by encrypting a second user identifier for the given user using an encryption key of the content platform and transmitting the subscription token to the publisher computing system.