GRID Security Review - Computer Network Security - page 105

ating system. Legion is an object-oriented meta-system and, thus, is based on the
principles of the object-oriented paradigm like inheritance, encapsulation and poly-
morphism [2] [6].
3.3.2 Proposed Security Architecture
The basic unit in a Legion system is the object. Each entity in the system, for example
processes, users, resources etc. is represented by an object. In order to provide secu-
rity in such a system one has, primarily, to protect these objects as well as the com-
munication among them.
The Legion Security Architecture is based on the following principles [6, 7]:
- The installation of Legion at a site should not compromise that site's security poli-
cies and goals.
- Legion must be configurable to the security needs of different organizations.
- Objects must have flexible access control mechanisms for authorizing and denying
method calls.
- Legion should protect identities, as well as, minimize the dispersion of authority
that delegation causes.
- The protection of integrity and privacy of underlying communications between
objects must be guaranteed.
In general, the primary goal for the Legion security architecture is to enable partici-
pants in a GRID system to expose their resources in a manner compliant with their
local policies. Next, we present the basic security mechanisms and policies that are
used by the Legion Security Architecture towards this goal [7].
3.3.2.1 Identity
Identity is important to higher-level security services, such as access control, and is
based on a unique, location-independent, Legion Object Identifier (LOID). By default
the Legion Security Architecture stores an RSA key pair in one of the LOID's fields.
This pair protects confidentiality and integrity of object communications through
encryption and digital signatures respectively. In fact, a LOID includes an empty,
unsigned X.509 certificate, which contains the key pair mentioned above. The X.509
certificate structure is used for two reasons: firstly, to enable the encoding of the key
pair in a standard way and, secondly, to provide the infrastructure for the incorpora-
tion of Certification Authorities on demand of the local system. By integrating keys
into LOIDs, Certification Authorities are rendered unnecessary although such an
authority is still useful for establishing user identities, as well as, eliminating some
kinds of public keys tampering.
3.3.2.2 Credentials
In a distributed object system the user may access resources indirectly thus requiring
corresponding objects to be able to perform actions on his behalf. Though intermedi-
ate objects could, in principle, be given the user's private key, the risk involved is
high. In order to eliminate that risk, Legion provides issuing of credentials to objects.
A credential is a list of rights granted by the user to a specific object for a specific
period of time. The latest poses a major concern as it actually defines the period dur-
ing which a credential is vulnerable to theft or abuse. The shorter the period the less
ease of use but the more secure way and vice versa.