Method and apparatus for authentication of client server communication

Abstract

The present invention provides a method and apparatus for message packet authentication to prevent the forging of message packets. After a message packet is created, a secret session key is preappended to the message, and a message digesting algorithm is executed on the altered message to create a message digest. A portion of the message digest, referred to as the signature, is then appended to the actual message when it is sent over the wire. The receiving station strips the signature from the message, preappends the same secret session key and creates its own message digest. The signature of the digest created by the receiving station is compared to the signature of the digest appended by the sending station. If there is a match, an authentic message is assumed. If there is no match, the message is considered as invalid and discarded. An advantage of the present invention is that the session key is never transmitted over the wire. The receiving station (server) already has the key and uses the key along with the message data to recalculate the message digest upon receiving the packet. The shared secret key (session key) is generated during initiation of the NCP session. In addition, cumulative state information is maintained by both the sending station and the receiving station. This state information is also used to authenticate messages.

Description

BACKGROUND OF THE INVENTION1. Field of the InventionThis invention relates to the field of network communications.2. Background ArtPersonal computers, or workstations, may be linked through a computer network to allow the sharing of data, applications, files, processing power, communications and other resources, such as printers, modems, mass storage and the like. Generally, the sharing of resources is accomplished the use of a network server. The server is a processing unit dedicated managing the centralized resources, managing data and sharing these resources with other PC's and workstations, often referred to as "clients". The server, network and PC's or workstations, combined together, constitute client / server computer network. An example of a client / server network model is illustrated in FIG. 1.FIG. 1 illustrates a client machine 101 coupled to a server macabre 102. The client machine 101 may be a PC, workstation, etc. The server machine may be a dedicated processor, PC, workst...

AI Technical Summary

Benefits of technology

dered as invalid and discarded. An advantage of the present invention is that the session key is never transmitted over the wire. The receiving station (server) already has the key and uses the key along with the message data to recalculate the message digest upon receiving the packet. The shared secret key (session key)is generated during initiation of the NCP session. In addition, cumulative state information is maintained by both the sending station and the receiving station. This state information is also used to authenticate messages.

Problems solved by technology

In addition, there may be certain types of files or activities that are restricted from most users.

For example, financial data is often restricted to users who have a need to know or use the financial data.

Generally, other users are not permitted to access that data.

However, that alone is not sufficient to enable an intruder to forge a message.

If not, it is an invalid request and the server discards the packet.

A problem is that depending on the size of the window for allowed retries, an intruder could randomly provide a correct sequence number within the window.

If the window is made smaller, legitimate transactions might be interrupted when the correct sequence number is not provided by a legitimate user.

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