29-10-2012, 01:12 PM
RFID TECHNOLOGY
[attachment=37275]
INTRODUCTION
Almost every product in the market has a barcode printed on it. Barcodes are machine-readable parallel bars that store binary information, revealing information about the product. Thus, it acts as the product fingerprint. As we go to the supermarket to buy things, the checkout person runs our selection over the scanner to scan the barcode, there’s an audible beep, and we are told how much money we owe.But the days of barcode are numbered. The reason is that a technology called radiofrequency identification (RFID) is catching on.RFID tags are being used by corporations to track people and products in just about every industry. They transform everyday objects like cargo containers, car keys, and even clothes on the rack at a shopping mall into mini nodes on a network. Databases then record the location and status of these network nodes to determine product movements. [4], [3]
TRANSPONDER
A tag is any device or label that identifies the host to which it is attached. It typically does not hinder the operation of the host or adversely affect its appearance.
The word transponder is derived from the words transmitter and responder. The tag responds to a transmitted or communicated request for the data it carries.
CLASSIFICATION OF TAGS
On the basis of the presence of battery, tags can be classified into active or passive tags.
Active tags are powered by an internal battery and are generally read/write devices. They contain a cell having a high power to weight ratio and are capable of operating over a temperature range of -50 to +70 degree Celsius. Active tags have a finite life time. A suitable cell coupled to suitable low power circuitry can ensure functionality of ten or more years depending on operating temperatures, read/write cycles and usage. They have greater size and increased cost compared to passive tags.
Passive tags operate without an internal battery source, deriving the power to operate from the field generated by the reader. They are hence lighter than active tags and have greater life time. They have shorter read ranges compared to active tags. They are also constrained in their ability to store data and perform well in electromagnetically noisy environments.[2],[5]
RFID tags can also be classified on the basis of coupling into inductively and capacitively coupled tags.
Inductively coupled RFID tags consist of the silicon microprocessor which vary in size depending on their purpose and metal coil which is made of copper or aluminum wire that is wound into a circular pattern on the transponder. This coil acts as the tag’s antenna. The tag transmits signal to the reader with the read distance determined by the size of the coil antenna. It also consists of an encapsulating material of glass or polymer that wraps around the chip and coil. Inductively coupled RFID tags are powered by the magnetic field generated by the reader .The tag’s antenna picks up the magnetic energy and the tag communicates with the reader. The tag then modulates the magnetic field in order to retrieve and transmit data back to the reader. Data which is transmitted back to the reader is directed to the host computer. These tags are expensive due to the silicon, the coil antenna and the process that is needed to wind the coil around the surface of the tag.
READER/INTERROGATOR
The reader/interrogators can differ considerably in complexity depending on the type of tags being supported and functions to be fulfilled. The overall function is to provide the means of communicating with the tag and facilitating data transfer. Functions performed by readers include signal conditioning, parity error checking and correction. Once the signal from a transponder has been correctly received and decoded, algorithms can be applied to decide whether the signal is a repeat transmission and may then instruct the transponder to stop transmitting. This is known as Command Response Protocol and is used to circumvent the problem of reading multiple tags in a short span of time. Using interrogators in this way is also referred to as Hands Down Polling. A more secure, but slower tag polling technique is called Hands Up Polling which involves the interrogator looking for tags with specific identities and interrogating them, in turn. A further approach uses multiple readers, multiplexed into one interrogator but results in cost increase.[6]
RANGE AND POWER LEVELS
The range that can be achieved in an RFID is determined by:
1. The power available at the reader/interrogator to communicate with the tags.
2. The power available within the tag to respond.
3. The environmental conditions and structures, the former being more significant at higher frequencies including the signal to noise ratio.
Although the level of available power is the primary determinant of range, the manner and efficiency in which that power is deployed also influences the range. The field or wave generated from an antenna extends into space surrounding it and its strength diminishes with respect to distance. The antenna design determines the shape of the field or propagating wave delivered so that range is also influenced by the angle subtended between the tag and antenna.
In the space free of any obstruction or absorption mechanism, the strength of field reduces in inverse proportion to the square of the distance. For a wave propagating through a region in which reflections can arise from the ground and from obstacles, the reduction in strength can vary as an inverse fourth power of the distance. Where different paths arise in this way, the phenomenon is called multi-path attenuation. At higher frequencies, moisture presence can cause absorption which can further affect the range. Where a number of reflective obstacles are to be encountered within the applications under consideration, which may vary from time to time, it may also be necessary to establish the implications of such changes through an appropriate environmental evaluation.
Possession
Authentication by means of possession is the most common method and will also be widely spread in future. The simplest implementation is the possession of a mechanical key. A much higher security is offered if the key contains an electronic tag such as a transponder. To start the vehicle, the mechanical key and the code in the transponder must match.
All cryptographic systems described above are based on static authentication procedures, that means the security system of the car can verify the identity of the key but the electronics in the key cannot check the identity of the communication partner. A mutual authentication procedure which also allows the key to verify the identity of the communication partner is one feature that would improve the security level of the system.
A much higher level of security can be achieved with a simple symmetrical algorithm known as challenge / response protocol. The security system of the vehicle can check the identity of the key by sending a question (a challenge) and verifying the answer (response). The correct answer can only be given if a secret is known that is shared by both partners. This challenge/response
concept has several advantages. During normal use, the secret is not exchanged and both challenge and response vary from cycle to cycle.[7]
Standard Security Architectures using RFID
Various security systems using RFID transponders have been established on the market.
Fixed Code Systems are the most commonly used. During initialization, the controller learns different identification codes stored in the transponders that belong to a vehicle. When the driver places the ignition key in the lock cylinder, the fixed code in the transponder is read and compared to the codes stored in the memory of the controller.
The level of security depends to a great extend on the type of transponder used. There are write once transponders on the market which are delivered unprogrammed. Programming is done by the user. Commercially available readers/writers allow to pick up the code in the transponder while away from the vehicle and to program an unprogrammed unit. Thus a copy of the fixed code has been generated which cannot be distinguished from the original. True Read Only systems on the market are factory programmed with a unique identification number. These systems do not allow copies. However, it is possible to emulate the data signal on the radio frequency level. The effort to design an emulator is considerable and requires RF design knowledge.
[attachment=37275]
INTRODUCTION
Almost every product in the market has a barcode printed on it. Barcodes are machine-readable parallel bars that store binary information, revealing information about the product. Thus, it acts as the product fingerprint. As we go to the supermarket to buy things, the checkout person runs our selection over the scanner to scan the barcode, there’s an audible beep, and we are told how much money we owe.But the days of barcode are numbered. The reason is that a technology called radiofrequency identification (RFID) is catching on.RFID tags are being used by corporations to track people and products in just about every industry. They transform everyday objects like cargo containers, car keys, and even clothes on the rack at a shopping mall into mini nodes on a network. Databases then record the location and status of these network nodes to determine product movements. [4], [3]
TRANSPONDER
A tag is any device or label that identifies the host to which it is attached. It typically does not hinder the operation of the host or adversely affect its appearance.
The word transponder is derived from the words transmitter and responder. The tag responds to a transmitted or communicated request for the data it carries.
CLASSIFICATION OF TAGS
On the basis of the presence of battery, tags can be classified into active or passive tags.
Active tags are powered by an internal battery and are generally read/write devices. They contain a cell having a high power to weight ratio and are capable of operating over a temperature range of -50 to +70 degree Celsius. Active tags have a finite life time. A suitable cell coupled to suitable low power circuitry can ensure functionality of ten or more years depending on operating temperatures, read/write cycles and usage. They have greater size and increased cost compared to passive tags.
Passive tags operate without an internal battery source, deriving the power to operate from the field generated by the reader. They are hence lighter than active tags and have greater life time. They have shorter read ranges compared to active tags. They are also constrained in their ability to store data and perform well in electromagnetically noisy environments.[2],[5]
RFID tags can also be classified on the basis of coupling into inductively and capacitively coupled tags.
Inductively coupled RFID tags consist of the silicon microprocessor which vary in size depending on their purpose and metal coil which is made of copper or aluminum wire that is wound into a circular pattern on the transponder. This coil acts as the tag’s antenna. The tag transmits signal to the reader with the read distance determined by the size of the coil antenna. It also consists of an encapsulating material of glass or polymer that wraps around the chip and coil. Inductively coupled RFID tags are powered by the magnetic field generated by the reader .The tag’s antenna picks up the magnetic energy and the tag communicates with the reader. The tag then modulates the magnetic field in order to retrieve and transmit data back to the reader. Data which is transmitted back to the reader is directed to the host computer. These tags are expensive due to the silicon, the coil antenna and the process that is needed to wind the coil around the surface of the tag.
READER/INTERROGATOR
The reader/interrogators can differ considerably in complexity depending on the type of tags being supported and functions to be fulfilled. The overall function is to provide the means of communicating with the tag and facilitating data transfer. Functions performed by readers include signal conditioning, parity error checking and correction. Once the signal from a transponder has been correctly received and decoded, algorithms can be applied to decide whether the signal is a repeat transmission and may then instruct the transponder to stop transmitting. This is known as Command Response Protocol and is used to circumvent the problem of reading multiple tags in a short span of time. Using interrogators in this way is also referred to as Hands Down Polling. A more secure, but slower tag polling technique is called Hands Up Polling which involves the interrogator looking for tags with specific identities and interrogating them, in turn. A further approach uses multiple readers, multiplexed into one interrogator but results in cost increase.[6]
RANGE AND POWER LEVELS
The range that can be achieved in an RFID is determined by:
1. The power available at the reader/interrogator to communicate with the tags.
2. The power available within the tag to respond.
3. The environmental conditions and structures, the former being more significant at higher frequencies including the signal to noise ratio.
Although the level of available power is the primary determinant of range, the manner and efficiency in which that power is deployed also influences the range. The field or wave generated from an antenna extends into space surrounding it and its strength diminishes with respect to distance. The antenna design determines the shape of the field or propagating wave delivered so that range is also influenced by the angle subtended between the tag and antenna.
In the space free of any obstruction or absorption mechanism, the strength of field reduces in inverse proportion to the square of the distance. For a wave propagating through a region in which reflections can arise from the ground and from obstacles, the reduction in strength can vary as an inverse fourth power of the distance. Where different paths arise in this way, the phenomenon is called multi-path attenuation. At higher frequencies, moisture presence can cause absorption which can further affect the range. Where a number of reflective obstacles are to be encountered within the applications under consideration, which may vary from time to time, it may also be necessary to establish the implications of such changes through an appropriate environmental evaluation.
Possession
Authentication by means of possession is the most common method and will also be widely spread in future. The simplest implementation is the possession of a mechanical key. A much higher security is offered if the key contains an electronic tag such as a transponder. To start the vehicle, the mechanical key and the code in the transponder must match.
All cryptographic systems described above are based on static authentication procedures, that means the security system of the car can verify the identity of the key but the electronics in the key cannot check the identity of the communication partner. A mutual authentication procedure which also allows the key to verify the identity of the communication partner is one feature that would improve the security level of the system.
A much higher level of security can be achieved with a simple symmetrical algorithm known as challenge / response protocol. The security system of the vehicle can check the identity of the key by sending a question (a challenge) and verifying the answer (response). The correct answer can only be given if a secret is known that is shared by both partners. This challenge/response
concept has several advantages. During normal use, the secret is not exchanged and both challenge and response vary from cycle to cycle.[7]
Standard Security Architectures using RFID
Various security systems using RFID transponders have been established on the market.
Fixed Code Systems are the most commonly used. During initialization, the controller learns different identification codes stored in the transponders that belong to a vehicle. When the driver places the ignition key in the lock cylinder, the fixed code in the transponder is read and compared to the codes stored in the memory of the controller.
The level of security depends to a great extend on the type of transponder used. There are write once transponders on the market which are delivered unprogrammed. Programming is done by the user. Commercially available readers/writers allow to pick up the code in the transponder while away from the vehicle and to program an unprogrammed unit. Thus a copy of the fixed code has been generated which cannot be distinguished from the original. True Read Only systems on the market are factory programmed with a unique identification number. These systems do not allow copies. However, it is possible to emulate the data signal on the radio frequency level. The effort to design an emulator is considerable and requires RF design knowledge.