Abstract: In one aspect, a computerized method for implementing user authentication using, device synchronization to match that includes the step of accessing a web page. The web page includes an agent. The computerized method includes the step of loading the agent in the background. The computerized method, includes the step of, generating, with the agent, an agent-generated token in background. The agent-generated token is encrypted as a cryptographic token. The computerized method includes the step of executing a deep link with the agent-generated token. The computerized method includes the step of sending the agent-generated token, a Universally unique identifier (UUID) and a private key in a hidden native application to an encrypted-token server. The computerized method includes the step of determining that the IP address pairs with the agent-generated token. The computerized method includes the step of receiving, with the native application, a call back.