This is a form of malware that attempts to extort money from its victims by holding their data to ransom until a fee is paid. A recent example is CryptoLocker, which securely encrypts the victim’s documents, offering a decryption key only when the ransom has been paid.
In computer graphics, a raster graphics image is a dot matrix data structure representing a generally rectangular grid of pixels, or points of colour, viewable via a monitor, paper, or other display medium. Raster images are stored in image files with varying formats.
What is a raster file?
Raster graphics are digital images created or captured (for example, by scanning in a photo) as a set of samples of a given space. A raster is a grid of x and y coordinates on a display space. (And for three-dimensional images, a z coordinate.)
What is the difference between raster and vector?
The difference between vector and raster graphics is that raster graphics are composed of pixels, while vector graphics are composed of paths. A raster graphic, such as a gif or jpeg, is an array of pixels of various colours, which together form an image.
What is a raster image made up of?
Raster graphics has origins in television technology, with images constructed much like the pictures on a television screen. A raster graphic is made up of a collection of tiny, uniformly sized pixels, which are arranged in a two-dimensional grid made up of columns and rows.
Also see: What are vector and raster maps?
A “raster map” is a data layer consisting of a gridded array of cells. It has a certain number of rows and columns, with a data point (or null value indicator) in each cell. These may exist as a 2D grid or as a 3D cube made up of many smaller cubes, i.e. a stack of 2D grids.
These can be created by high-end and enthusiast cameras and certain Nokia Lumia smartphones. They contain picture data taken directly from the image sensor in the camera prior to conversion to the more compact JPEG format. As such, they contain more picture information and can allow for higher-quality images to be processed later on your computer. They also require specialised software to process them and take up considerably more disk space. The actual format of the data is often unique to the specific model of camera used.
An RCA connector, sometimes called a phono connector or Cinch connector, is a type of electrical connector commonly used to carry audio and video signals. The connectors are also sometimes casually referred to as A/V jacks. The name “RCA” derives from the Radio Corporation of America, which introduced the design by the early 1940s for internal connection of the pickup to the chassis in home radio-phonograph consoles. It was originally a low-cost, simple design, intended only for mating and disconnection when servicing the console. Refinement came with later designs, although they remained compatible.
RCA connectors began to replace the older quarter-inch phone connectors for many other applications in the consumer audio world when component high-fidelity systems started becoming popular in the 1950s. However, quarter-inch phone connectors are still common in professional audio, while miniature phone connectors (3.5 mm) have become predominant in personal stereo systems.
Retina Display is a marketing term developed by Apple to refer to devices and monitors that have a resolution and pixel density so high – roughly 300 or more pixels per inch – that a person is unable to discern the individual pixels at a normal viewing distance.
In terms of displays, the screen resolution is a measure of the amount of detail which can be shown. Either in terms of the absolute number of pixels in an image, such as 1920×1080 or in terms of the number of pixels contained within a certain area – often expressed as pixels per inch (ppi). Apples Retina displays offer a resolution high enough to exceed the resolution of the human visual system, thereby rending individual pixels invisible and making screen elements appear smooth rather than blocky.
Resonant inductive coupling or electrodynamic induction is the near field wireless transmission of electrical energy between two magnetically coupled coils that are part of resonant circuits tuned to resonate at the same frequency.
This process occurs in a resonant transformer, an electrical component which consists of two high Q coils (see Q factor) wound on the same core with capacitors connected across the windings to make two coupled LC circuits. Resonant transformers are widely used in radio circuits as bandpass filters, and in switching power supplies. Resonant inductive coupling is also being used in wireless power systems. Here the two LC circuits are in different devices; a transmitter coil in one device transmits electric power across an intervening space to a resonant receiver coil in another device. This technology is being developed for powering and charging portable devices such as cellphones and tablet computers at a distance, without being tethered to an outlet.
Resonant transfer works by making a coil ring with an oscillating current. This generates an oscillating magnetic field. Because the coil is highly resonant, any energy placed in the coil dies away relatively slowly over very many cycles; but if a second coil is brought near it, the coil can pick up most of the energy before it is lost, even if it is some distance away. The fields used are predominantly non-radiative, near fields (sometimes called evanescent waves), as all hardware is kept well within the 1/4 wavelength distance they radiate little energy from the transmitter to infinity.
One of the applications of the resonant transformer is for the CCFL inverter. Another application of the resonant transformer is to couple between stages of a superheterodyne receiver, where the selectivity of the receiver is provided by tuned transformers in the intermediate-frequency amplifiers.
Rooting a phone provides the user with full, unrestricted control over all aspects of the operating system. Prior to rooting, many configuration options are deliberately unavailable to the user in order to prevent possible damage to the operating system or even the hardware. Sometimes functions are disabled to ensure that certain preinstalled apps or settings are not tampered with by the user. This is similar to the concept of ‘Jailbreaking’ on iOS, although Android imposes far fewer restrictions on the user by default and therefore rooting is usually required only for very specific tasks.
This is a malicious piece of software installed on a computer system to give privileged access levels to unauthorised individuals. The name is a combination of ‘root’, the name given to the administrative user on most Unix-like operating systems, and ‘kit’ as it usually comprises a selection of ready-made tools to make the software easy to deploy. Rootkits typically employ stealth techniques to avoid detection by their victims, but can be picked up and eliminated by effective antivirus software.
RSA is one of the first practical public-key cryptosystems and is widely used for secure data transmission. In such a cryptosystem, the encryption key is public and differs from the decryption key which is kept secret. In RSA, this asymmetry is based on the practical difficulty of factoring the product of two large prime numbers, the factoring problem. RSA is made of the initial letters of the surnames of Ron Rivest, Adi Shamir, and Leonard Adleman, who first publicly described the algorithm in 1977. Clifford Cocks, an English mathematician working for the UK intelligence agency GCHQ, had developed an equivalent system in 1973, but it was not declassified until 1997.
A user of RSA creates and then publishes a public key based on two large prime numbers, along with an auxiliary value. The prime numbers must be kept secret. Anyone can use the public key to encrypt a message, but with currently published methods, if the public key is large enough, only someone with knowledge of the prime numbers can feasibly decode the message. Breaking RSA encryption is known as the RSA problem; whether it is as hard as the factoring problem remains an open question.
RSA is a relatively slow algorithm, and because of this it is less commonly used to directly encrypt user data. More often, RSA passes encrypted shared keys for symmetric key cryptography which in turn can perform bulk encryption-decryption operations at much higher speed.