526 Chapter 5—Mobile IPv6
case, we need to check only one of them. The procedure when returning to home is discussed
in Section 5.5.7.
A mobile node computes a hash value using the secret information computed above. The
algorithm is as follows:
Mobility Data = the care-of address of a mobile node
| the address of a correspondent node
| the Mobility Header message
Authenticator = First(96, HMAC_SHA1(K
bm
, Mobility Data))
where,
‘|’ denotes concatenation of data,
‘the Mobility Header message’ is either a Binding Update
or a Binding Acknowledgment message,
First(x, y) function returns the first x bits from y,
HMAC_SHA1(key , data) computes a HMAC SHA-1 hash value
against ‘data’ using ‘key’ as a key.
The hash value is called an Authenticator. The original data ...