The Wiegand interface is a
de facto
''De facto'' ( ; , "in fact") describes practices that exist in reality, whether or not they are officially recognized by laws or other formal norms. It is commonly used to refer to what happens in practice, in contrast with ''de jure'' ("by la ...
wiring standard which arose from the popularity of
Wiegand effect card readers in the 1980s. It is commonly used to connect a card swipe mechanism to the rest of an
access control system. The sensor in such a system is often a "Wiegand wire", based on the Wiegand effect, discovered by
John R. Wiegand. A Wiegand-compatible reader is normally connected to a Wiegand-compatible security panel.
Physical layer
The Wiegand interface uses three wires, one of which is a common ground and two of which are data transmission wires usually called DATA0 and DATA1, alternatively labeled "D0" and "D1" or "Data Low" and "Data High". When no data is being sent, both DATA0 and DATA1 are
pulled up to the "high" voltage level — usually +5 VDC. When a 0 is sent the DATA0 wire is pulled to a low voltage while the DATA1 wire stays at a high voltage. When a 1 is sent the DATA1 wire is pulled to a low voltage while DATA0 stays at a high voltage.
The high signaling level of 5 VDC is used to accommodate long cable runs from card readers to the associated access control panel, typically located in a secure closet. Most card reader manufacturers publish a maximum cable run of . An advantage of the Wiegand signalling format is that it allows very long cable runs, far longer than other interface standards of its day allowed.
Protocol
The communications protocol used on a Wiegand interface is known as the Wiegand protocol. The original Wiegand format had one parity bit, 8 bits of facility code, 16 bits of ID code, and a trailing parity bit for a total of 26 bits. The first parity bit is calculated from the first 12 bits of the code and the trailing parity bit from the last 12 bits. However, many inconsistent implementations and extensions to the basic format exist.
Many access control system manufacturers adopted Wiegand technology, but were unhappy with the limitations of only 8 bits for site codes (0-255) and 16 bits for card numbers (0-65535), so they designed their own formats with varying complexity of field numbers and lengths and parity checking.
The physical size limitations of the card dictated that a maximum of 37 Wiegand wire filaments could be placed in a standard credit card, as dictated by CR80 or
ISO/IEC 7810 standards, before misreads would affect reliability. Therefore, most Wiegand formats used in physical access control are less than 37 bits in length.
See also
*
Access badge
*
Access control
In the fields of physical security and information security, access control (AC) is the selective restriction of access to a place or other resource, while access management describes the process. The act of ''accessing'' may mean consuming ...
*
Keycard lock
*
Common Access Card
*
Credential
*
Identity document
An identity document (also called ID or colloquially as papers) is any documentation, document that may be used to prove a person's identity. If issued in a small, standard credit card size form, it is usually called an identity card (IC, ID c ...
*
Magnetic stripe card
*
Photo identification
Photo identification or photo ID is an identity document that includes a photograph of the holder, usually only their face. The most commonly accepted forms of photo ID are those issued by government authorities, such as driver's licenses, ident ...
*
Security
Security is protection from, or resilience against, potential harm (or other unwanted coercive change) caused by others, by restraining the freedom of others to act. Beneficiaries (technically referents) of security may be of persons and social ...
(
physical
Physical may refer to:
*Physical examination
In a physical examination, medical examination, or clinical examination, a medical practitioner examines a patient for any possible medical signs or symptoms of a medical condition. It generally co ...
,
engineering
Engineering is the use of scientific method, scientific principles to design and build machines, structures, and other items, including bridges, tunnels, roads, vehicles, and buildings. The discipline of engineering encompasses a broad rang ...
)
*
Proximity card
*
Security
Security is protection from, or resilience against, potential harm (or other unwanted coercive change) caused by others, by restraining the freedom of others to act. Beneficiaries (technically referents) of security may be of persons and social ...
*
Smart card
A smart card, chip card, or integrated circuit card (ICC or IC card) is a physical electronic authentication device, used to control access to a resource. It is typically a plastic credit card-sized card with an embedded integrated circuit (IC) c ...
References
{{reflist
External links
Open Security Research - Hacking the Wiegand Serial ProtocolSIA Standard, AC-01-1996.10 - Access Control - Wiegand
LayerOne 2007 - Zac Franken - Wiegand Hacked (Video on Youtube)* [http://appft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PG01&p=1&u=/netahtml/PTO/srchnum.html&r=1&f=G&l=50&s1=20070046424.PGNR.&OS=DN/20070046424 US Patent, Device Authentication Using a Unidirectional Protocol]
US Patent, Secure Wiegand Communications
Contactless smart cards
Data transmission