Service access method and system, authentication method and system, client and authentication server

The invention provides a service access method, a service access system, an authentication method, an authentication system, a client and an authentication server. The specific content is that: the authentication server generates and stores a service password corresponding to a user account according to the user account, a sequence number and an identifier of terminal equipment which are submitted by the client; when a subsequent user requests for service access, the client generates a service password corresponding to the user account according to the user account, the sequence number and the identifier of the terminal equipment, and indicates the authentication server to authenticate according to the pre-stored service password and the service password generated by the client; the service password is relevant to the identifier of the terminal equipment in which the client is positioned and relevant to the sequence number, the identifier of the terminal equipment is difficult to steal maliciously and the sequence number has longer bits from 64 to 128 and is difficult to peep, so the safety of accessed service can be improved by adopting the scheme of the embodiment of the invention.