Access control

People use rules to stay safe.

Access control is a way to decide who can enter a place. It can also decide who can use a digital resource.

In the past, people used metal keys and locks. A key opens a door for the person holding it. But keys can be lost or copied. They also cannot track when someone used them.

Today, many places use electronic access control. This system uses computers to help. A person shows a credential to a reader. A credential is something you have, like a smart card. It can also be something you know, like a PIN code. It can even be something you are, like a fingerprint.

The reader sends information to a control panel. This panel is a reliable processor. It checks an access control list to see if you are allowed. If the list says yes, the panel unlocks the door.

To stay extra safe, some use two-factor authentication. This means you must provide two different things to get in. For example, you might use a card and a PIN. This makes it much harder for the wrong person to enter.

Access control is a way to decide who can enter a place or use a resource. It helps keep buildings and digital information safe. This process can mean letting someone in or stopping them from entering. In the digital world, this is sometimes called admission control. It is a very important part of keeping things private. Organizations use special rules called access policies to keep their data safe.

Physical access control works by checking who, where, and when someone enters. In the past, people used mechanical locks and metal keys. A person with a key can open a door, but keys can be easily copied. They also do not keep a record of who used them. Today, many places use electronic access control to solve these problems. This system uses computers to check if a person is allowed to enter.

An electronic system works in a few clear steps. First, a person shows a credential to a reader near a door. A credential is something you have, like a smart card, or something you know, like a PIN. The reader sends a number to a control panel. This panel is a reliable processor that checks an access control list. If your name is on the list, the panel unlocks the door. If not, the door stays locked and the system records the attempt.

To make things even safer, people use two-factor authentication. This means you must provide two different types of proof to get in. One type is something you know, such as a password or a PIN. Another type is something you have, like a key fob or an access badge. You can also use something you are, which is called a biometric. Biometrics include things like your fingerprint, your face, or even your voice.

Modern systems use many different parts to work together. A system might include a reader, a control panel, and locking hardware like electric door strikes. Some readers are very smart and can make decisions all by themselves. Other readers are basic and just send information to a main hub. In 2009, most systems used a "hub and spoke" setup with a central control panel. Now, many new systems use internet connections to talk to a computer directly.

Access control, or AC, is the process of deciding if a subject should be granted or denied access to an object. An object can be a physical place or a digital resource. Accessing something might mean entering a room, using a tool, or consuming data. In digital environments, this is often called admission control. It is a vital part of maintaining privacy and security. Organizations create access control policies to manage these decisions. These policies are part of a larger security policy designed to match an organization's risk appetite.

Physical access control manages who, where, and when someone enters or exits. Historically, this relied on mechanical locks and keys. While effective, mechanical systems have significant limitations. Keys can be easily copied or transferred to unauthorized people. They also do not provide records of which specific key was used. Furthermore, mechanical locks cannot restrict access to specific times or dates. If a key is lost, the entire lock must be re-keyed to maintain security.

Electronic access control (EAC) uses computers to solve the weaknesses of mechanical systems. EAC allows for complete authentication, authorization, and accounting. The process begins when a user presents a credential to a reader. A credential is a physical object, a piece of knowledge, or a biological trait. The reader sends this information, usually as a number, to a control panel. This control panel is a highly reliable processor. It compares the number against an access control list. If there is a match, the panel operates a relay to unlock the resource. If the request is denied, the resource remains locked and the attempt is recorded.

To improve security, systems often use multi-factor authentication. A single factor can be subverted if a credential is stolen or shared. To prevent this, two-factor authentication requires two different types of proof. There are three main types of authenticating information. First is something the user knows, such as a PIN or password. Second is something the user has, like a smart card or key fob. Third is something the user is, which refers to biometric measurements. Biometrics include fingerprints, facial recognition, iris scans, or voice patterns.

A complete access control system consists of several integrated components. These include the control panel, the entry point, and the reader. The entry point might be a door, a turnstile, or a parking gate. Locking hardware, such as electromagnetic locks or electric door strikes, secures the entry. A magnetic door switch is often used to monitor the position of the door. For safety, systems include Request-to-exit (RTE) devices. These allow people to leave during emergencies, such as a fire. This can be done through a button, a motion detector, or via mechanical free egress.

Readers are classified by how much intelligence they possess. Basic readers are non-intelligent; they simply forward a card number or PIN to a control panel. Semi-intelligent readers can control door hardware but cannot make access decisions themselves. If the connection to the main controller fails, these readers may stop working. Intelligent readers are more advanced because they have their own memory and processing power. They can make access decisions independently. A new generation called IP readers connects directly to a host computer using a network.

System topology describes how these components are connected. Around 2009, the predominant setup was the hub and spoke model. In this model, a central control panel acts as the hub. The readers act as the spokes and communicate via a serial connection, often RS-485. This standard is useful because it allows for long cable runs of up to 4,000 feet. However, technology is shifting toward the edge. Modern manufacturers are placing controllers directly at the door. These IP-enabled controllers connect to databases using standard networks, making the system more decentralized.