Protocols for Secure Communication in Wireless Sensor Networks

158 Chapter 6. Integrity-Preserving Communications
Definition 6.2. Key authentication is the property whereby one party is assured
that no other party aside from a specifically identified second party (and possibly
additional identified trusted parties) may gain access to a particular secret
key.
Definition 6.3. Data origin authentication is a type of authentication whereby
a party is corroborated as the (original) source of specified data created at some
(typically unspecified) time in the past.
Definition 6.4. Data integrity is the property whereby data has not been altered
in an unauthorized manner since the time it was created, transmitted, or stored
by an authorized source.
In the course of this work, we most often refer to “messages” instead of
“data”. As a message, we understand a container for data, which is represented
in some encoded form. However, in many cases these terms are used interchangeably.
Also, we talk about “hosts” or “nodes” instead of “parties”, but
these terms are used interchangeably.
There are a variety of methods for entity and message authentication being
used. In the physical world, biometric techniques are used for authenticating
human beings: Fingerprints may be used for entity authentication, while voice
recognition is commonly used for entity and message authentication (over the
phone, for exmple). In electronic communication systems, cryptographic, keybased
methods are required. Standard mechanisms for authentication include
digital signatures and message authentication codes (cf. 2.8.2).
Maintaining data integrity is often achieved through mechanisms like redundant
storage or checksums. This is sufficient to counter unsystematic errors
which occur in natural phenomena like fatigue of material or random interference.
In cases where data integrity is threatened by a skillful, malicious adversary,
this is not sufficient. In such a case, data origin authentication through
cryptographic means is used to detect unauthorized tampering with data. There
is no known cryptographic primitive, which can be used to ensure integrity
(against malicious adversaries) without recourse to authentication.
It has to be stressed that node authentication alone does not guarantee correctness.
A compromised node may correctly report its identity and authenticate
its message as it is expected from a correctly operating node. However, the
data it reports may be manipulated, and there may be no way of detecting such
manipulations. This is the reason why node capture attacks are so powerful.
The last two definitions will be the most important ones for this work, and
both data integrity and data origin authentication (also called message authen-