នៅ​ជិត​វាល​គមនាគមន៍

**Near field communication** (**NFC**) គឺជាសំណុំនៃស្ដង់ដារបស់ទូរស័ព្ទឆ្លាតវៃ និង ឧបករណ៍ដទៃទៀតដែលធ្វើការទំនាក់ទំនងដោយរលកវិទ្យុ ដោយគ្រាន់តែដាក់ឧបករណ៍នោះជិតគ្នា ឬ ប៉ះគ្នា ដែលចម្ងាយជាមធ្យមគឺប៉ុន្មានសង់ទីម៉ែត្រ (៣សង់ទីម៉ែត្រ)។ កម្មវិធីដែលបានបង្កើតឡើងសម្រាប់ប្រើប្រាស់ជាមួយនឹង NFC រួមមានការផ្ទេរទិន្នន័យ ការតំឡើងទំនាក់ទំនង Wi-Fi  ការភ្ជាប់ទំនាក់ទំនងអាចធ្វើឡើងបានដោយឧបករណ៍ដែលមានNFC និង unpowered NFC chip ដែលហៅថា "tag".

ស្តង់ដារសប់ NFC រួមមាន protocols ទំនាក់ទំនង និងទំរង់នៃការផ្លាស់ប្ដូរព័ត៌មានដែលយោងតាមរលកវិទ្យុស្ដង់ដាដែលមានហើយ radio-frequency identification (RFID) ដូចជាISO/IEC 14443 និង FeliCa. ស្ដង់ដារួមមាន ISO/IEC 18092 និងស្ដង់ដាដទៃទៀតដែលមានក្នុងវេទិកាពិភាក្សាអំពី NFC ដែលបានបង្កើតឡើងនៅឆ្នាំ២០០៤ដោយ Nokia Philips​ និង​ Sony ហើយបច្ចុប្បន្នមានសមាជិកជាង១៦០។ វេទិកាពិភាក្សានោះក៏បានផ្សព្វផ្សាយពីបច្ចេកវិទ្យា NFC និង អាជ្ញាបណ្ណលើឧបករណ៍ដែលប្រើប្រាស់បច្ចេកទេសនេះ

'[[]]'''== Uses ==

NFC builds upon RFID systems by allowing two-way communication between endpoints, where earlier systems such as contactless smart cards were one-way only. Since unpowered NFC "tags" can also be read by NFC devices,
Germany,
Austria,
Finland,
New Zealand, and
Italy have trialed NFC ticketing systems for public transport.

India is implementing NFC based transactions in box offices for ticketing purposes.

### Bluetooth and Wi-Fi connections 
NFC offers a low-speed connection with extremely simple setup, and can be used to bootstrap more capable wireless connections. For example, the Android Beam software uses NFC to complete the steps of enabling, pairing and establishing a Bluetooth connection when doing a file transfer. Nokia has used NFC technology to pair Bluetooth headsets and speakers with one tap in its NFC-enabled devices. The same principle can be applied to the configuration of Wi-Fi networks.

### Social networking 
NFC can be used in social networking situations, such as sharing contacts, photos, videos or files, and entering multiplayer mobile games.

### Identity and access tokens 
The NFC Forum promotes the potential for NFC-enabled devices to act as electronic identity documents and keycards.

## History 
NFC traces its roots back to radio-frequency identification, or RFID. RFID allows a reader to send radio waves to a passive electronic tag for identification, authentication and tracking.
* 1983 The first patent to be associated with the abbreviation RFID was granted to Charles Walton.
*1995 wallet paying and receiving electronic, described in the report and annexes describing the invention of Gaston Schwabacher in 0017 patented protocol 24/01/1995 at INPI Brazil with the IP number 9500345
* 2004 Nokia, Philips and Sony established the Near Field Communication (NFC) Forum
* 2006 Initial specifications for NFC Tags
* 2006 Specification for "SmartPoster" records
* 2006 Nokia 6131 was the first NFC phone
* 2009 In January, NFC Forum released Peer-to-Peer standards to transfer contact, URL, initiate Bluetooth, etc.
* 2010 Samsung Nexus S: First Android NFC phone shown
* 2011 Google I/O "How to NFC" demonstrates NFC to initiate a game and to share a contact, URL, app, video, etc.
* 2011 Research In Motion is the first company for its devices to be certified by MasterCard Worldwide, the functionality of PayPass
* 2012 March. EAT, a well known UK restaurant chain and Everything Everywhere (Orange Mobile Network Operator) partner on the UK's first nationwide NFC enabled smartposter campaign. (lead by Rene' Batsford, Head of ICT for EAT, also known for deploying the UK's first nationwide contactless payment solution in 2008) A specially created mobile phone app is triggered when the NFC enabled mobile phone comes into contact with the smartposter.
* 2012 Sony introduces the "Smart Tags", which use NFC technology to change modes and profiles on a Sony smartphone at close range, included in the package of (and "perfectly paired" with) the Sony Xperia P Smartphone released the same year.
* 2012 Samsung introduces TecTile; a set of MIFARE NFC stickers and a companion application for Android to read and write the TecTile stickers, and design macros that can be triggered by them.

## Essential specifications 
NFC is a set of short-range wireless technologies, typically requiring a distance of 10 cm or less. NFC operates at 13.56&nbsp;MHz on ISO/IEC 18000-3 air interface and at rates ranging from 106 kbit/s to 424 kbit/s. NFC always involves an initiator and a target; the initiator actively generates an RF field that can power a passive target. This enables NFC targets to take very simple form factors such as tags, stickers, key fobs, or cards that do not require batteries. NFC peer-to-peer communication is possible, provided both devices are powered.

NFC tags contain data and are typically read-only, but may be rewriteable. They can be custom-encoded by their manufacturers or use the specifications provided by the NFC Forum, an industry association charged with promoting the technology and setting key standards. The tags can securely store personal data such as debit and credit card information, loyalty program data, PINs and networking contacts, among other information. The NFC Forum defines four types of tags that provide different communication speeds and capabilities in terms of configurability, memory, security, data retention and write endurance. Tags currently offer between 96 and 4,096 bytes of memory.

* As with proximity card technology, near-field communication uses magnetic induction between two loop antennas located within each other's near field, effectively forming an air-core transformer. It operates within the globally available and unlicensed radio frequency ISM band of 13.56&nbsp;MHz. Most of the RF energy is concentrated in the allowed 7&nbsp;kHz bandwidth range, but the full spectral envelope may be as wide as 1.8&nbsp;MHz when using ASK modulation.
* Theoretical working distance with compact standard antennas: up to 20&nbsp;cm (practical working distance of about 4 cm)
* Supported data rates: 106, 212 or 424 kbit/s (the  bit rate 848 kbit/s is not compliant with the standard ISO/IEC 18092)
* There are two modes:
** Passive communication mode: The initiator device provides a carrier field and the target device answers by modulating the existing field. In this mode, the target device may draw its operating power from the initiator-provided electromagnetic field, thus making the target device a transponder.
** Active communication mode: Both initiator and target device communicate by alternately generating their own fields. A device deactivates its RF field while it is waiting for data. In this mode, both devices typically have power supplies.

* NFC employs two different codings to transfer data. If an active device transfers data at 106 kbit/s, a modified Miller coding with 100% modulation is used. In all other cases Manchester coding is used with a modulation ratio of 10%.
* NFC devices are able to receive and transmit data at the same time. Thus, they can check for potential collisions, if the received signal frequency does not match with the transmitted signal's frequency.

## Comparison with Bluetooth 
NFC and Bluetooth are both short-range communication technologies that are integrated into mobile phones. As described in technical detail above, NFC operates at slower speeds than Bluetooth, but consumes far less power and doesn't require pairing. 

NFC sets up more quickly than standard Bluetooth, but has a lower transfer rate than Bluetooth low energy. With NFC, instead of performing manual configurations to identify devices, the connection between two NFC devices is automatically established quickly: in less than a tenth of a second. The maximum data transfer rate of NFC (424 kbit/s) is slower than that of Bluetooth V2.1 (2.1 Mbit/s). With a maximum working distance of less than 20&nbsp;cm, NFC has a shorter range, which reduces the likelihood of unwanted interception. That makes NFC particularly suitable for crowded areas where correlating a signal with its transmitting physical device (and by extension, its user) becomes difficult.

In contrast to Bluetooth, NFC is compatible with existing passive RFID (13.56&nbsp;MHz ISO/IEC 18000-3) infrastructures. NFC requires comparatively low power, similar to the Bluetooth V4.0 low energy protocol. When NFC works with an unpowered device (e.g., on a phone that may be turned off, a contactless smart credit card, a smart poster), however, the NFC power consumption is greater than that of Bluetooth V4.0 Low Energy, since illuminating the passive tag needs extra power.
;ISO/IEC 21481 / ECMA-352: *Near Field Communication Interface and Protocol-2* (NFCIP-2)

NFC incorporates a variety of existing standards including ISO/IEC 14443 both Type A and Type B, and FeliCa. NFC enabled phones work basically, at least, with existing readers. Especially in "card emulation mode" a NFC device should transmit, at a minimum, a unique ID number to an existing reader.

In addition, the NFC Forum has defined a common data format called NFC Data Exchange Format (NDEF), which can store and transport various kinds of items, ranging from any MIME-typed object to ultra-short RTD-documents, such as URLs.

The NFC Forum added the Simple NDEF Exchange Protocol to the spec that allows sending and receiving messages between two NFC-enabled devices.

### GSMA 
The GSM Association (GSMA)  is the global trade association representing nearly 800 mobile phone operators and more than 200 product and service companies across 219 countries. Many of its members have led NFC trials around the World and are now preparing services for commercial launch.

GSM is involved with several initiatives:
* Standard setting: GSMA is developing certification and testing standards to ensure the global interoperability of NFC services.
* On November 17, 2010, after two years of discussions, AT&T, Verizon and T-Mobile launched a joint venture intended to develop a single platform on which technology based on the Near Field Communication (NFC) specifications can be used by their customers to make mobile payments. The new venture, known as ISIS, is designed to usher in the broad deployment of NFC technology, allowing NFC-enabled cell phones to function similarly to credit cards for the 200 million customers using cell phone service provided by any of the three carriers throughout the United States.

### StoLPaN 
StoLPaN ('Store Logistics and Payment with NFC') is a pan-European consortium supported by the European Commission's Information Society Technologies program. StoLPaN will examine the as yet untapped potential for the new kind of local wireless interface, NFC and mobile communication.

### NFC Forum 
The NFC Forum is a non-profit industry association formed on March 18, 2004, by NXP Semiconductors, Sony and Nokia to advance the use of NFC short-range wireless interaction in consumer electronics, mobile devices and PCs. The NFC Forum promotes implementation and standardization of NFC technology to ensure interoperability between devices and services. As of March 2011, the NFC Forum had 135 member companies.

### Alternative form factors 
To realize the benefits of NFC in cellphones not yet equipped with built in NFC chips a new line of complementary devices were created. MicroSD and UICC SIM cards were developed to incorporate industry standard contactless smartcard chips with ISO14443 interface, with or without built-in antenna. The microSD and SIM form factors with built-in antenna have the great potential as bridge devices to shorten the time to market of contactless payment and couponing applications, while the built in NFC controllers gain enough market share.

### Other standardization bodies 
Other standardization bodies that are involved in NFC include:
* ETSI / SCP (Smart Card Platform) to specify the interface between the SIM card and the NFC chipset.
* GlobalPlatform to specify a multi-application architecture of the secure element.
* EMVCo for the impacts on the EMV payment applications

## Security aspects 
Although the communication range of NFC is limited to a few centimeters, NFC alone does not ensure secure communications. In 2006, Ernst Haselsteiner and Klemens Breitfuß described different possible types of attacks, and detail how to leverage NFC's resistance to man-in-the-middle attacks to establish a specific key., Unfortunately, as this technique is not part of the ISO standard, NFC offers no protection against eavesdropping and can be vulnerable to data modifications. Applications may use higher-layer cryptographic protocols (e.g., SSL) to establish a secure channel.

### Eavesdropping 
The RF signal for the wireless data transfer can be picked up with antennas. The distance from which an attacker is able to eavesdrop the RF signal depends on numerous parameters, but is typically a small number of metres. Also, eavesdropping is highly affected by the communication mode. A passive device that doesn't generate its own RF field is much harder to eavesdrop on than an active device. An attacker can typically eavesdrop within 10m and 1m for active devices and passive devices, respectively. For this attack the adversary has to forward the request of the reader to the victim and relay back its answer to the reader in real time, in order to carry out a task pretending to be the owner of the victim's smart card. This is similar to a man-in-the-middle attack. For more information see a survey of practical relay attack concepts. One of libnfc  code examples demonstrates a relay attack  using only two stock commercial NFC devices. It has also been shown that this attack can be practically implemented using only two NFC-enabled mobile phones.

### Lost property 
Losing the NFC RFID card or the mobile phone will open access to any finder and act as a single-factor authenticating entity. Mobile phones protected by a PIN code acts as a single authenticating factor. A way to defeat the lost-property threat requires an extended security concept that includes more than one physically independent authentication factor.

### Walk-off 
Lawfully opened access to a secure NFC function or data is protected by time-out closing after a period of inactivity.  Attacks may happen despite provisions to shut down access to NFC after the bearer has become inactive. The known concepts described primarily do not address the geometric distance of a fraudulent attacker using a lost communication entity against lawful access from the actual location of the registered bearer. Additional features to cover such an attack scenario dynamically shall make use of a second wireless authentication factor that remains with the bearer in case of the lost NFC communicator. Relevant approaches are described as an electronic leash or its equivalent, a *wireless key.*

## NFC-enabled handsets 
In 2011, handset vendors released more than 40 NFC-enabled handsets. Notably absent among them was Apple with its iPhone; version 6 of its iOS mobile operating system does not support NFC. According to a *Wall Street Journal* article, today's Apple prefers not to be in a first mover position.  Google, on the other hand, includes NFC functionality in their Android mobile operating system and provides a NFC payment service, Google Wallet. BlackBerry devices have also supported NFC using BlackBerry Tag on a number of devices running BlackBerry OS 7.0 and greater. Mastercard has added further NFC support for PayPass for the Android and BlackBerry platforms, enabling PayPass users to make payments using their Android or BlackBerry smartphones. Microsoft added native NFC functionality in their mobile OS with Windows Phone 8, as well as the Windows 8 operating system. Microsoft provides the "Wallet hub" in Windows Phone 8 for NFC payment, and can integrate multiple NFC payment services within a single application.

## Deployment 
, several hundred NFC trials have been conducted. Some firms have moved to full-scale service deployments, spanning either a single country or multiple countries. Multi-country deployments include Orange's rollout of NFC technology to banks, retailers, transport, and service providers in multiple European countries, and Airtel Africa and Oberthur Technologies deploying to 15 countries throughout Africa.

## មើលផងដែរ 
* CIPURSE
* FeliCa
* MIFARE
* M-Pesa
* Near and far field
* Object hyperlinking
* Poken
* RFID
* RuBee
* Single Wire Protocol
* TransferJet
* UICC configuration
* Wii U GamePad

## កំណត់ចំណាំ
## ឯកសារយោង
* 
* 

## អានបន្ថែម
* Near Field Communication (NFC) Technology and Measurements 

## តំណភ្ជាប់ខាងក្រៅ 
* A day at MIT with Near-Field Communication
* About NFC Antennas
* Future of Near Field
* ISO/IEC 18092:2004
* Mobile phones hope to be 'smart wallet'
* Near Field Communications in the security industry&nbsp;— Access Control with mobile phones
* NFC technology
* Preparing for the NFC revolution
* Open source NFC plugin for Eclipse