Access Control System

In computer security, discretionary access control (DAC) is a kind of access control defined by the Trusted Computer System Evaluation Criteria as "a means of restricting access to objects based on the identity of subjects and/or groups to which they belong.

The controls are discretionary in the sense that a subject with a certain access permission is capable of passing that permission (perhaps indirectly) on to any other subject.

However, the meaning of the term in practice is not as clear-cut as the definition given in the TCSEC standard.

For example, the term is commonly used in contexts that assume that, under DAC, every object has an owner that controls the permissions to access the object, probably because many systems do implement DAC using the concept of an owner. But the TCSEC definition does not say anything about owners, so technically an access control system doesn't have to have a concept of owner to meet the TCSEC definition of DAC.

As another example, Capability system are sometimes described as providing discretionary controls because they permit subjects to transfer their access to other subjects, even though capability-based security is fundamentally not about restricting access "based on the identity of subjects". (Capability systems do not, in general, allow permissions to be passed "to any other subject"; the subject wanting to pass its permissions must first have access to the receiving subject, and subjects do not generally have access to all subjects in the system.)

Discretionary access control is commonly defined in opposition to mandatory access control Occasionally a system as a whole is said to have "discretionary" or "purely discretionary" access control as a way of saying that the system lacks mandatory access control. On the other hand, systems can be said to implement both MAC and DAC simultaneously, where DAC refers to one category of access controls that subjects can transfer among each other, and MAC refers to a second category of access controls that imposes constraints upon the first.

With the card access syste, it is easy to enter a door with a RFID card rather than a conventional key. It is a great benefits of suc system as we are now able to access multiple door with just one card. It gives the card issuer a greater control measure.

Currently doing on the topic of class 1 UHF . There were many times I came across the gen 1 or 2 tags therefore I have decided to find the difference.


What is the difference between EPC’s Gen 1 tags and Gen 2 tags?

With regard to Generation 1, there are Class 0 and Class 1 specifications for tags in the UHF band. Class 0 was originated as a protocol by Matrics Technology Systems (acquired by Symbol Technologies) and Class 1 was originated as a protocol by Alien Technologies. Class 0 has been defined by EPCglobal as a read-only device. Class 1 is defined in the EPCglobal specification as a tag that is one-time programmable. In practice, the products that are available from Alien Technologies are reprogrammable. And Matrics/Symbol has released “Class 0+” products, which are based on the same protocol as the Class 0 device, but are, in fact, fully re-writable.

With regard to Generation 2, Class 1 (Class 0 was dropped) standards were ratified at the end of 2004 as a response to the limitations of the Generation 1 standards. Gen 2 provides expanded data functionality and better performance, is designed to support EPC codes up to 256 bits long, and has the provision for extra data to be carried in the tag based on a single RFID protocol. In addition, G2 tags should be comparable with regard to radio frequencies (from 860 MHz to 960 MHz) globally, allowing tags to work consistently in different countries under differing emissions standards. Tags must be able to understand three different approved modulation schemes as well as be able to transmit at several different speeds or data rates. In addition, Gen 2 includes a method to support “dense-interrogator channelized signaling” (also called “dense reader mode”), which attempts to reduce interference among readers to make it less likely that reader signals will impede tag signals. An in-depth analysis of the differences between Generation 1 and Generation 2 protocols is discussed in Zebra's white papers Managing the EPC Generation Gap and Gen 2 Implications for smart Label Printing.


http://www.smartcodecorp.com/faq/index.htm#What_is_RFID

A website to share. It has different kind of question that people may just ask.

What is EPC ?

EPC stands for Electronic Product Code. It was conceptualized by the Auto ID Center at MIT. This organization developed the concept during an ambitious project meant to enable the identification of all physical objects. In a supply chain context this meant tracking of every manufactured unit on a global scale using unique serialized identifiers (license plates).

This concept came complete with the idea of have a global extranet managed by a global entity, a global entity responsible for managing and assigning unique ranges of identifiers to the manufacturer’s of the world (similar to the Uniform Code Council), an Object Naming Service, Physical Markup Language, a specific format of data for the serialized identifier (EPC), and a means by which the RFID tag communicates with an interrogator (air interface). The goal was to create an Internet of physical objects.

The Electronic Product Code is a unique identification scheme that contains four distinct partitions:

Header

EPC Manager (manufacturer or entity responsible for maintaining Object Class and Serial Number)

Object Class (Item Number or SKU, or alternatively Lot Number)

Serial Number (within Object Class)

This data structure is currently supported in several Classes of EPC and is available in more than one length scheme. For example there are 64 bit and 96 bit versions of EPC. Other versions include data capacities of differing sizes and types. Wal-Mart has focused on the use of a minimum of 96 bit EPC codes. This size may be increased with the pending Class 1 Generation 2 specification.

An example of a 96 bit EPC code

It has been estimated that using this identification scheme one could uniquely identify every grain of rice on Earth.

A few of the most recently visible EPC Classes for Ultra-High frequency (915 MHz), Passive RFID tags are described below:

EPC Class 0 is a read-only specification where the EPC code would be encoded at time of RFID tag manufacture.

EPC Class 0+ is an write once, read many version of EPC Class 0 from the same RFID manufacturer.

EPC Class 1 (or EPC Class 1, Version 1) is a write once, read many version of EPC from a different manufacturer.

EPC Class 1 Generation 2 is a specification that is currently being drafted and reviewed via EPC Global, Inc. with input from major manufacturers, retailers, and government bodies. The specification is not yet written or finalized but it is the specification that Wal-Mart and the Department of Defense have targeted for their current RFID mandate.

There are other classes pertaining to High Frequency (13.56 MHz) passive, write/read many passive, semi active and active tags. These specifications exist but have not been the focus of such retail giants as Wal-Mart and Target.

This website provides the suppliers that provides EPC Class 1 compliance UHF tags (:

http://www.rfidsolutionsonline.com/IndustrySearch/SearchResults.aspx?keyword=UHF+RFID+Tags&TabIndex=0&image1.x=26&image1.y=15&VNETCOOKIE=NO