contain the same amount of information as the original message. An example would be a refresh message that is equivalent to a create message. This property allows a refresh message to create state along a new path, where no previous state is available. For this to work, specific classes of cryptographic mechanisms supporting this behavior are needed. An example is a scheme based on digital signatures, which, however, should be used with care due to possible denial of service attacks.
Problems with the usage of public-key-based cryptosystems in protocols are described in [AN97] and in [ALN00].
In addition to the threat scenario described above, an incoming signaling message might trigger communication with third-party nodes such as policy servers, LDAP servers, or AAA servers. If an adversary is able to transmit a large number of signaling messages (for example, with QoS reservation requests) with invalid credentials, then the verifying node may not be able to process other reservation messages from legitimate users.
4.3. Eavesdropping and Traffic Analysis
This section covers threats whereby an adversary is able to eavesdrop on signaling messages. The signaling packets collected may allow traffic analysis or be used later to mount replay attacks, as described in Section 3.2. The eavesdropper might learn QoS parameters, communication patterns, policy rules for firewall traversal, policy information, application identifiers, user identities, NAT bindings, authorization objects, network configuration and performance information, and more.
An adversary's capability to eavesdrop on signaling messages might violate a user's preference for privacy, particularly if unprotected
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