Abstract: A system for serving targeted advertisements while protecting privacy receives an item of personally identifiable information (PII) from a person using a browser. The item of PII may be, for example, a telephone number or email address. The item of PII is hashed, then used to look up a node in an identity graph corresponding to the person. The node contains a link uniquely associated with the person, which is returned in an encrypted form. An envelope is created that contains the link, and is set as a first-party cookie on the person's browser. When the person uses the browser to visit another website the envelope is decrypted, and the link is separately encrypted using a different method for each of a plurality of DSPs to which the link is sent. The DSPs are used to set a display advertisement on the user's browser, the process occurring in real time.