Avaya Configuring Data Encryption Services Manuel d'utilisateur télécharger pdf (Page 24)

Configuring Data Encryption Services

1-8 117386-A Rev. A

Master Encryption Key (MEK)

The MEK encrypts the Trafﬁc Encryption Key (TEK). The LTSS for a circuit,

combined with the current time, is the source of its MEK. You do not actually

generate, enter, or view the MEK. The WEP software automatically calculates this

value. Like the LTSS, the MEK must be the same on each end of a link.

An MEK periodically changes according to the value of the MEK Change

parameter.

For the encryption software to generate identical MEKs, and for the MEKs to

remain identical on both sides of a link as their values change, they must change at

approximately the same time. That can only happen if

• The MEK Change parameter is set to the same value on each end of a link.

For more information on conﬁguring this key change attribute, refer to

ppendix A, “Encryption Parameters.”

• The clocks on both routers are synchronized. For further information about

router clocks in relation to encryption, see the section “Synchronizing Router

Clocks” in Cha

pter 2.

Trafﬁc Encryption Key (TEK)

The TEK encrypts the data that travels across the network. The RNG on a

transmitting router creates the TEK. WEP then encrypts the TEK, using the MEK.

At the receiving router, WEP decrypts the TEK, and uses it to decrypt the data.

The TEK that the standard encryption software generates is 40 bits long. The

Strong Encryption Option (SEO) can generate both 40-bit and 56-bit TEKs.

The TEK automatically changes according to the values in the TEK Change Time

and TEK Change Bytes parameters. A sending router generates a new TEK, and

WEP encrypts it. The receiving router notes the change, decrypts it, replaces the

old TEK with the new one, and uses the new one to decrypt current and future data

until the TEK changes again.

Each router has its own TEK and TEK Change attributes that it uses to protect

data that it sends. A link therefore has two TEKs which are different, and which

change independently of each other. For more information on conﬁguring key

change attributes, refer to A

ppendix A, “Encryption Parameters.”

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Avaya Configuring Data Encryption Services Manuel d'utilisateur Page 24