Qlogic iSR6142 Guia do Utilizador descarregar pdf (Página 113)

SN0054660-00 A 5-1

5 Configuring CHAP

This chapter describes CHAP and provides the procedures for configuring CHAP

using the SANsurfer Router Manager.

For procedures, see the following sections:

 “Discovery Session—Bi-directional CHAP” on page 5-2

 “Discovery Session—Uni-directional CHAP” on page 5-3

 “Normal Session—Bi-directional CHAP” on page 5-3

 “Normal Session—Uni-directional CHAP” on page 5-4

CHAP Definition

In challenge handshake authentication protocol (CHAP), the authentication agent

sends the client program a random value that is used only once and an ID value.

Both the sender and peer share a predefined secret. The peer concatenates the

random value, the ID, and the secret, and calculates a one-way hash using MD5

(Message-Digest algorithm 5). It sends the hash value to the authenticator, which

in turn builds that same string on its side, calculates the MD5 checksum, and

compares the result with the value received from the peer. If the values match, the

peer is authenticated.

By transmitting only the hash, the secret cannot be reverse-engineered. The ID

value is increased with each CHAP dialogue to protect against replay attacks.

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Qlogic iSR6142 Guia do Utilizador Página 113