Sovis, PavolKohlar, FlorianSchwenk, JörgFreiling, Felix C.2019-01-172019-01-172010978-3-88579-264-2https://dl.gi.de/handle/20.500.12116/19793OpenID is a user-centric and decentralized Single Sign-On system. It enables users to sign into Relying Partiesby providing an authentication assertion from an OpenID Provider. It is supported by many leading internet companies and there are over a billion accounts capable of using OpenID. We present a security analysis of OpenID and the corresponding extensions and reveal several vulnerabilities. This paper demonstrates how identity information sent within the OpenID protocol can be manipulated, due to an improper verification of OpenID assertions and no integrity protection of the authentication request.enText/Conference Paper1617-5468