Systems and methods for authenticating a user requesting access to a resource in a cloud-computing system. The methods comprise, by a resource service: receiving an access request for accessing a resource associated with the resource service from a computing device associated with a user, determining context information corresponding to the access request, and using the determined context information for identifying an authentication protocol for authenticating the user. The authentication protocol includes at least one authentication scheme. The methods further comprise generating an authentication challenge and transmitting the authentication challenge to the computing device. The authentication challenge includes an initial token and authentication parameters corresponding to the identified authentication protocol.