Information Technology Reference
In-Depth Information
3.3.2.3 Authentication
Authentication in the Legion system is realized through the use of credentials. When a
requestor object wants to communicate with a target object then it casts an authentica-
tion credential, which is nothing more than the LOID of the target object signed by
the requestor object.
3.3.2.4 Access Control
In a Legion system, access is the ability to call a method on an object. Access control
is decentralized and each object is responsible for enforcing its own access control
policy. In general all method calls to an object must first pass through the access con-
trol procedure (called “the MayI layer”) before the target method (member function)
is invoked. Only if the caller has the appropriate rights for the target method will the
access control allow the method invocation to proceed.
3.3.2.5 Communications
A method call from one object to another can consist of multiple messages. These
messages use one of a number of underlying transport layers (UDP/IP, TCP/IP) or
platform-specific message passing services and must be transmitted without their
unauthorized disclosure or modification occurring. A message may be sent three
ways: in the
clear mode
, in
protected mode
or in
private mode
. In clear mode no en-
cryption or other security mechanism is applied to the message. In protected mode a
message digest is generated in order to protect its integrity. Finally, in private mode
the message is encrypted.
3.3.2.6 Object Management
As stated in section 3.3.1 the Legion system is implemented as a middleware over
existing operating systems that have their own security mechanisms and policies.
Therefore, it is crucial for the Legion system to be implemented in such a way that
ensures its security policies and the OS's security policies do not compromise each
other.
3.4
The Globe Security Architecture
3.4.1 Globe
Globe stands for
Gl
obal
O
bject
B
ased
E
nvironment. As its name reveals it is a wide-
area distributed system, which was developed in order to constitute a middleware
level between the operating system and the application level, exactly as Legion does.
The main characteristics of the Globe system are [10]:
-
It is a uniform model for the support of distributed systems.
-
It supports a flexible implementation framework.
-
It is highly scalable.
Globe is based on Distributed Shared Objects (DSOs). A DSO is formed by the repli-
cation of a local object, which resides in a single address space to other address
spaces, and is identified by a unique Object ID (OID). Each local object consists of
five sub-objects: Semantics, Control, Replication, Communication and Security sub-
