1. A method of determining whether a user of a mobile device corresponds to a previously authenticated user, the previously authenticated user having been previously authenticated using an identity document, the method comprising: accessing, by a chip reader associated with the mobile device, an integrated circuit component of an identity document; retrieving, by the chip reader from the integrated circuit component, digital image data indicative of a digital image of the previously authenticated user; capturing, using a camera associated with the mobile device, an image comprising image data, wherein the image corresponds to the user of the mobile device; comparing the retrieved digital image data to the image data; determining, based on the comparing of the retrieved digital image data to the image data, whether the captured image and the digital image represent the same user; determining whether the retrieved digital image data is valid using a public key; and forming an association between the previously authenticated user and the mobile device when it is determined that (i) the retrieved digital image data is valid and (ii) the captured image and digital image represent the same user; the method further comprising: retrieving signed data from the integrated circuit component of the identity document, and wherein the determining whether the retrieved digital image data is valid comprises: hashing the retrieved digital image data; comparing the hashed digital image data to the signed data; verifying the authenticity of the signed data using the public key; and determining that the retrieved digital image data is valid when (i) the hashed digital image data corresponds to the signed data; and (ii) the signed data is authenticated by the public key.