el tema del rinde, porque no van a tener el mismo rinde todos los años.

The conditions under which readers query tags are a significant determinant of an RFID system’s technology requirements. The most important parameters regarding the RFID transaction environment include:

 The distance between the reader and the tag,

 The amount of time in which a transaction must be completed, and

 Whether or not the reader has access to a network and can use the network to store related data. Sections 3.3.1 through 3.3.3 discuss these parameters.

3.3.1 Distance between Reader and Tag

Distance requirements often determine the type of tag that can be deployed. The distance between the reader and the tag also has security implications. In general, longer distances between the reader and the tag could make it easier for an adversary to eavesdrop on their communications. Longer distances also allow an adversary to use their own reader to perform unauthorized transactions more easily (as discussed in Section 2.3.3.3).

In some cases, the RFID system designer has considerable latitude in setting the distance between reader and tag. For example, an application controlling access to a garage might require drivers to place an RFID-enabled badge within inches of a reader or it might require a general proximity of several feet to a

RFID-enabled transponder within the vehicle. The choice is essentially an application design decision that may include such factors as cost and convenience.

In other cases, the distance between reader and tag is dictated by the environment in which the RFID system will be deployed. For example, a toll payment application that identifies vehicles on a highway may require that readers query tags from a distance of several meters. In this case, the minimum read distance is a requirement for the design of the RFID system.

3.3.2 Transaction Speed

Transaction speed can be measured in a variety of ways. A common metric is the number of tags read per second. The main reasons why an application has requirements related to the speed of transactions are:

 Readers are expected to communicate with multiple tags nearly simultaneously and cannot do so if each transaction takes longer than a certain period of time.

 Tagged items are in motion and only reside in a reader’s operating range for a limited period of time.  The system’s users may perceive the application as a nuisance if transactions take longer than a short

period of time to complete.

For example, in some inventory applications, operators may need to confirm the entire inventory at the end of each business day. In this case, each transaction must be completed within a small fraction of a second or the process may take too long to finish. Similar issues may arise when trying to read the tags of athletes in a tracking system designed to measure race times. In this case, if the transactions take too long, there is a chance that some participants in the race may go out of range before the reader identifies them.

Many security mechanisms introduce latency into RFID transactions. Additional steps are needed to perform authentication, encryption, cover-coding, and other security-related procedures. Each additional step takes time. When considering security controls, organizations need to balance the business impact of each security control’s effect on transaction speed with the protection it provides.

3.3.3 Network Connectivity and Data Storage

Whether or not an RFID system’s readers are networked with database applications has major

implications for the architecture of the RFID system and its security. When an application needs to link data with tags, the data needs to be stored somewhere. If the readers are networked with databases, then the data can be stored in the databases. Otherwise, the data must be stored on the tags.

When data is stored centrally on database servers, the tag only needs to contain an identifier, which links the tag to its associated information. In this architecture, the vast majority of the data processing occurs on the supporting systems to which the reader is connected. On the other hand, when data is stored on tags, the tags must have some form of memory and support both write and read transactions.

Regardless of where data is stored, the data’s integrity must be protected. If the data is sensitive, its confidentiality must also be protected. The methods for achieving this include authentication, access control, encryption, and physical security. However, database servers and tags implement these methods in different ways. Nearly all commercial database servers support a wide variety of configurable security controls, but most tags do not. In general, RFID systems that use networked readers to access database

SECTION 3:RFIDAPPLICATIONS AND APPLICATION REQUIREMENTS

servers are preferable to those that store data on tags, both in terms of cost and security. However, a system may require local storage of data on tags for several reasons, including:

 Extending the network to a remote RFID reader is not feasible or is more expensive than using tags that support the required functionality.

 Accessing the data from the network introduces unacceptable latency.

 Network availability is inherently poor, perhaps as a result of harsh operating conditions, which makes accessing data on tags a more reliable approach.

 The participants in an open system have determined that the risk of storing data on tags is less than the risk of opening their networks to external entities.

 Each tag must collect and store information from a sensor or other data source before it can communicate with a networked reader.

 Users want control over when personal data is shared and therefore prefer that it remain on the tag and not in an enterprise database.