Chapter 7 Security

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out the entire system or into the application layer. Having security as part of the

message also makes it possible to persist both the message data and its security

information. For example, perhaps to prove that a message was sent, an applica 

tion may need to persist the message data and the digital signature bound to the

message. Or, to protect against internal threats, an application may need to keep

data in a SOAP message confidential, even to the application layer. HTTPS, since

it only protects a message during transport, cannot give the application layer this

encryption protection for the data.

7.4.2.2

Peer Entity and Data Origin Authentication

Two kinds of authentication in a network are: peer entity authentication and data

origin authentication. With peer entity authentication, the security service verifies

that the identity of a peer in an association such as a session between a sender and

receiver is the identity claimed. Note that there must be an association between the

two parties.

Data origin authentication verifies that the original source of a received

message is as claimed, but, unlike peer entity authentication, no association

between the sender and receiver is required. With data origin authentication, a

target receiver can verify the identity of a message as belonging to the original

message creator even if the message passes from its initial source through multi 

ple participants before arriving at the target receiver. 

A Web service interaction that uses HTTPS supports peer entity authentica 

tion, because the interaction covers just the connection between two peers.

Message level security supports data origin authentication, since its security is

tied to the SOAP message itself rather than the transport mechanism.

Using HTTPS is disadvantageous in multi hop scenarios where a message

passes through numerous intermediate participants between the initial sender and

target receiver, because each message exchange requires establishing a new asso 

ciation between the communicating participants. Furthermore, SSL requires that

each participant decrypt each received message, then encrypt the same message

before transmitting it to the next participant in the workflow. SSL, relying on peer

entity authentication, does not support end to end multi hop message exchange.

(See Figure 7.6.)