A method for authenticating a user's request to access information managed by a server system from a first client device, the method comprising: at the server system, the server system having one or more processors and memory for storing programs to be executed by the one or more processors: receiving an information access request from the first client device in response to the user requesting access information associated with a user account; in response to the information access request, generating a unique identifier and returning the unique identifier to the first client device, wherein the unique identifier is to be displayed on a display of the first client device, the unique identifier comprises first authentication information generated by the server system for the information access request, and the first authentication information is encoded in the unique identifier; receiving a first message from a second client device, wherein the first message comprises user account information at the server system and second authentication information; determining whether the second authentication information corresponds to the unique identifier generated by the server system, which comprises: determining whether the second authentication information extracted from the unique identifier by the second client device is the same as the first authentication information encoded into the unique identifier; and if the second authentication information is the same as the first authentication information encoded into the unique identifier generated by the server system, authenticating the information access request received from the first client device, such that the user can access information at the server system and be associated with the user account information. at the server system, the server system having one or more processors and memory for storing programs to be executed by the one or more processors: receiving an information access request from the first client device in response to the user requesting access information associated with a user account; in response to the information access request, generating a unique identifier and returning the unique identifier to the first client device, wherein the unique identifier is to be displayed on a display of the first client device, the unique identifier comprises first authentication information generated by the server system for the information access request, and the first authentication information is encoded in the unique identifier; receiving a first message from a second client device, wherein the first message comprises user account information at the server system and second authentication information; determining whether the second authentication information corresponds to the unique identifier generated by the server system, which comprises: determining whether the second authentication information extracted from the unique identifier by the second client device is the same as the first authentication information encoded into the unique identifier; and if the second authentication information is the same as the first authentication information encoded into the unique identifier generated by the server system, authenticating the information access request received from the first client device, such that the user can access information at the server system and be associated with the user account information. receiving an information access request from the first client device in response to the user requesting access information associated with a user account; in response to the information access request, generating a unique identifier and returning the unique identifier to the first client device, wherein the unique identifier is to be displayed on a display of the first client device, the unique identifier comprises first authentication information generated by the server system for the information access request, and the first authentication information is encoded in the unique identifier; receiving a first message from a second client device, wherein the first message comprises user account information at the server system and second authentication information; determining whether the second authentication information corresponds to the unique identifier generated by the server system, which comprises: determining whether the second authentication information extracted from the unique identifier by the second client device is the same as the first authentication information encoded into the unique identifier; and if the second authentication information is the same as the first authentication information encoded into the unique identifier generated by the server system, authenticating the information access request received from the first client device, such that the user can access information at the server system and be associated with the user account information.