AP Spoofing in IEEE 802.11 Network.

AP Spoofing in IEEE 802.11 Network.

The access point spoofing (AP Spoofing) is a typical man-in-the middle attack. The attacker suits himself between two nodes and controls all the traffic between them in this attack. This threat is very dangerous as the attacker is able to catch all the information traveling across the network. It is not so easy rather complex to make a man-in-the-middle attack in a wired network because this would require real access to the network. But there is no need of physical existence in wireless network and so preferred by the attacker. The first step is to set up a rogue AP for association between a victim node and legitimate AP. Then the rogue AP is established by copying all the configuration of the legitimate one: SSID, MAC address etc.

The next step is to wait for a new user trying to connect to the network where it gets connection with the rogue AP. The users can connect by themselves with the rogue AP or the attacker can create a denial of service attack to the legitimate AP to interrupt connections and automatically new users get into trap with the rogue AP. In IEEE 802.11 networks, the subscriber nodes select AP by the strength of the receiving signal. The attacker only need to do is to ensure that his AP has greater signal strength as seen by the victim. To accomplish that, the attacker tries to place his AP nearer to the victim than the legitimate AP, or to use a different technique by using directional antennas. The rogue access point is shown in figure below.

Figure: Access Point Spoofing by a Rogue Node.

Thus the victim node gets connection to the rogue AP and continues its works as it does with the legitimate AP since it does not know the real fact. The attacker captures all the necessary information’s starting from passwords when the victim tries to login for different accesses. Getting all the required information’s the attacker achieves the ability to penetrate the legitimate network.

This attack is possible in IEEE 802.11 network because it doesn’t have strong two-way authentication between AP and nodes. AP credentials are usually broadcasted across the network for subscriber nodes. As a result eavesdropping the network becomes easy for the attacker and he can get all the information needed. The user nodes may use WEP authentication to authenticate themselves to the AP which is also vulnerable but still more secure. An attacker needs to eavesdrop a lot of traffic and try cryptanalysis in order to get the password.

Learn QR CODE

QR Code:

A QR Code (abbreviated from Quick Response Code) is a matrix barcode, also known as a two-dimensional code.

Quick response (QR) codes are among the latest in the stable of marketing tools. These have been devised to effectively bridge the gap between offline and online marketing. QR code was created by Toyota’s subsidiaryDenso Wave in 1994 to track vehicles during the manufacturing process and was initially confined to the automotive industry. With the evolution of smartphones, users got a mobile QR code reader in their pocket, which they could use to scan and read QR codes easily.

Note: To scan the image above, download the free QR reader application on your iPhone or Android device.

What is it?

QR Code, a registered trademark of Denso Wave Inc., is an enhancement over the conventional bar codes placed on objects such as product packaging or containers.

Bar codes store a smaller amount of information than QR codes because these store information only in the horizontal direction. A bar code scannerreads only the width and space between vertical lines and the vertical space (second dimension) is wasted.

QR code vs traditional bar code

In QR codes (2D codes), information is stored in both vertical and horizontal directions. So these can store the same amount of data as a bar code in only a tenth of the space.

A QR code may contain a huge amount of complicated numeric, alphanumeric or binary data. Storing up to 4296 characters, QR codes are internationally standardized under ISO 18004.

The technology of dots

The smallest square dot or pixel element of a QR code is called a module. As with bar codes, it is recommended to have an empty area around the graphic, which makes it easier for devices to read the QR code. This quiet area is ideally four modules wide. The minimum dimensions of a QR code depend upon the resolving power of the cameras that are used to scan the code. According to a Kaywa whitepaper, it is recommended to use a minimum size of 32×32 mm2 (1.25×1.25 inch2), excluding quiet zone, for QR codes that contain a URL. This guarantees that all camera phones can properly read the QR code. The above rule applies to perfectly printed codes that the user has direct access to.

For good reader accuracy, good contrast between the background and the dots colour is very important. The dots should be dark in colour and placed on a light background. The printing specifications of a QR code recommend a high dpi and solid colours.

How it works

A QR code system includes a QR code printer and a QR code scanner. To generate QR code, one needs a special printer and QR code creation software. Applying the right size to the QR code is important to make the code readable.

There are various factors which should be considered while determining the size of a QR code: Symbol version, data capacity, character type, error-correction level and module size based on printer performance.

Symbol version. QR codes have symbol versions from 1 to 40. Each version is differentiated by the number and configuration of modules. ‘Module’ refers to the B&W dots that constitute a QR code. Each version has a maximum data capacity that is decided by the amount of data, the type of characters (numeric, alphanumeric, etc.) and the error-correction level. So the more the data stored, the bigger the size of the QR code.

Error-correction level. QR codes have four levels of error-correction capability, viz, level L, M, Q and H in ascending order. With error correction, the user can read and retrieve data from a damaged QR code.

It is possible to create artistic QR Codes that still scan correctly, but contain intentional errors to make them more readable or attractive to the human eye, as well as to incorporate colours, logos and other features into the QR Code block.

Artistic QR code

Encryption

Although encrypted QR Codes are not very common, there are a few implementations. An Android app, for example, manages encryption and decryption of QR codes using DES algorithm (56 bits). Japanese immigration use encrypted QR Codes when placing visas in passports. 

Parity Check

How they work: parity checks in computer memory

Computers have internal checks to ensure they are working correctly. This article covers checks using a scheme called parity bits to ensure that the computer’s memory is accurate. 

It is important for the computer to know of memory failures, to avoid operating on bad data. An undetected memory failure could be catastrophic. Memory is hardware and does fail from time to time. This article is the second in the series on memory. 

 

Parity’s purpose

Memory parity is what helps the computer system detect that its memory has failed. If there is a problem with memory and the value of memory changes, parity can detect the problem and stop the computer. 

 

How parity works

Recall that memory is organized in bytes, which is eight bits. I When memory is manufactured, an additional bit is added to each byte. This is called the parity bit. The actual size of each memory location is therefore nine bits, but the computer only uses eight of the nine bits for data. The parity bit is checked and never sent to the rest of the computer. 

 

Writing parity

Every time a memory address is written, the parity circuit checks each bit of the byte. It counts all 1 bits in the byte. The sum of the 1 bits results either in an even or odd number. 

 

To continue, we must know whether the designers of the memory used even or odd parity. The circuit will work either way. Let’s assume they used even parity. Stay with me; we’re almost there. 

 

The parity bit is then set to a 0 or a 1 depending on the following. 

 

·         If the sum of the 1 bits is an even number, the parity bit will be written as a 0. This keeps the parity even, or keeps the sum of all 1 bits an even number. 

·         If the sum of the 1 bits is an odd number, the parity bit will be written as a 1. This keeps the parity even, or keeps the sum of all 1 bits an even number. 

 

Reading parity

If you haven’t seen the purpose yet, keep reading. After parity is written, the sum of all the bits, including the parity bit, will be even. Then when the given address is read later, its parity is checked by summing all 1 bits including the parity bit. The result better be an even number, or there is a problem. 

 

Examples

Here are a couple of examples of memory values and their parity bits. 

 

 

Notice that the total sum of all bits for each memory value is always an even number.