Verification helps to ensure the correctness of the model. In the code synthesis phase, the software part of the system model is synthesized to cyclic code. We propose an algorithm which can generate high-performance cyclic code from a model which describes the business work-flow. This feature significantly simplifies program development. A set of tools is implemented to support our design flow and they are successfully applied to an industrial case study for a PLC Programmable Logic Controller system which is used to control several physical devices in a huge palace.
- Home Birth: The Politics of Difficult Choices!
- Cyclic and Computer Generated Designs.
- cibd: Program for Constructing Cyclic Incomplete Block Designs.
- Donate to arXiv.
- Light Scattering in Solids I.
- Fundamentals of Organizational Communication.
DOI: Need Help? In accordance with an aspect of the present invention, a capability is provided that enhances the security of data received by a receiver. By providing this authentication, the receiver of the data can feel secure in acting on the data e. In one example, the data security capability includes encoding the data with one or more cyclic redundancy checks CRCs , transmitting the encoded data to a receiver, and decoding by the receiver the data in order to use the CRCs to authenticate the data.
A CRC used for data integrity ensures that the data received is the same as the data sent. The data and CRC can be known i. In contrast, a CRC for data security is used to indicate whether the data is transmitted by an authorized user or whether the data is authorized i. One embodiment of an environment incorporating and using one or more aspects of the present invention is depicted in FIG.
In one example, a transmitter is coupled to a receiver via a connection In the example described herein, connection is a wireless connection, and the transmitter is remote from the receiver. Many other variations are also possible and are considered a part of the claimed invention. Transmitter may be of various types of transmitting units.
As one example, transmitter includes a device FIG. One example of such a device is a field communications device, which is remote from the receiver, and is used by, for instance, a field engineer to transmit commands to a control system. Many types of field communications devices can be used, including palm devices, laptop computers or notebook computers.
In accordance with an aspect of the present invention, device is coupled to a CRC generator employed to encode the transmission from the device.
Cyclic Redundancy Check and Modulo-2 Division - GeeksforGeeks
For instance, the CRC generator receives clear data i. The CRC generator may be a part of the device or separate therefrom. In one example, the CRC generator is coupled to a random selection unit used to randomly select a CRC polynomial to be used to generate a CRC word used in encoding the transmission, as described in further detail below. Random selection unit may be a part of CRC generator or separate therefrom.
Receiver receives the encoded data from the transmitter.
Similar to the transmitter, receiver may be of various types of receiving units. As one example, the receiver includes a receiver control system , such as a control system for a utility or power facility or for a water plant.
The control system is capable of receiving commands e. As one example, the receiver control system is coupled to an actuator used to control physical devices, such as for instance, a pressure valve in a water filtration system. Receiver control system is further coupled to a CRC generator The CRC generator receives the encoded data from the transmitter, decodes the encoded data returning it to its clear state, and forwards the clear data to the receiver control system, assuming the CRC check is valid.
CRC generator may be a part of receiver control system or separate therefrom. In one example, CRC generator is coupled to a random selection unit , which is used in selecting the appropriate CRC polynomial to decode the encoded data, as described in further detail below. However, the functions that each perform at any particular time depend on whether it is acting as a transmitter or receiver. The CRC generator includes circuitry to add one or more cyclic redundancy checks to encode the data or to remove the one or more cyclic redundancy checks to decode the data.
There are several criteria for selecting a CRC polynomial, which determine characteristics of the length of the data word and a degree of desired security. By applying the cyclic redundancy check to the data, the only way to generate a correctly transmitted message is to know the correct data stream and the CRC polynomial in use.
Thus, attempts to break into the system through random transmissions result in failure of the CRC check, thus detecting the break-in. Various embodiments are possible to encode a transmission with one or more CRCs to provide data security. For example, a fixed CRC word can be added to a clear communication. To increase this initial security, selection of the CRC word is randomized.
There are, for instance, two techniques for randomizing the CRC word selection. The first technique includes using a synchronized clock by the transmitter and receiver which acts as an initial seed in a random number generator. That is, the transmitter and receiver select an identical random number for a given transmission. This technique further includes choosing a fixed clock resolution e. A second technique includes using an on-demand random generator in the transmitter to randomly select a random number for a given transmission. The random number is selected and then communicated to the receiver.
The transmitter and receiver configure the CRC circuitry identically for a given message, and each message generates an alternate configuration. By using a random number to select different CRC polynomials, security is increased. For example, assume a set of 16 polynomials is used to select CRC coding randomly for a given message. If the clear text and polynomial set are known, it will take, on average, eight random tries to generate the correct message.
Although security is enhanced, it still can be further improved. As one example, a plurality of CRCs are applied to the data. Referring to FIG. Horizontal CRC generator includes, for instance, a plurality of generators used to generate a plurality of CRCs for a particular message. In the example depicted herein, there are eight generators , and therefore, horizontal generator accepts as input 8 bit data from the device. Thus, each byte of data from an N byte message is input to the generator, such that each bit of the data byte is input into a respective horizontal CRC generator based on its position.
For instance, bit 0 of each byte is input to a first generator ; bit 1 of each byte is input to a second generator ;. Each generator receives N bits of data e. Thus, an output of each generator is an N bit data stream plus a CRC word. The chosen polynomial is selected from a plurality of polynomials that have been selected based on a set of criteria.
For example, as the degree of the polynomial determines the length of the CRC, for these implementations, degree 8 polynomials are selected giving 8 bit CRC characters for serial and parallel implementations. Another characteristic of the polynomial is that the exponent determines the capability of error detection and correction.
The greater the degree of correction and detection, the more difficult it would be to randomly create the correct data and CRC word. A careful selection of polynomials with good error detection and correction characteristics implies that these polynomials will perform better in a data security application. Thus, polynomials with a larger exponent are to be selected, in this embodiment. Ritter, Dr. Dobb's Journal of Software Tools, February. HTM—pages , which is hereby incorporated herein by reference in its entirety.
- Ebook Cyclic And Computer Generated Designs.
- Viruses in Human Gene Therapy?
- Networking For Dummies, 7th Edition;
- Molecular Mechanisms of Adult Stem Cell Aging (Else Kroner-Fresenius-Symposia, Vol. 1).
The plurality of polynomials is input to a random number generator The random number generator is used to randomly select a particular polynomial from the plurality of polynomials e. Since there are eight horizontal generators i. In one example, each horizontal generator includes circuitry to implement the various polynomials. Thus, the data bit stream being fed into the horizontal generator is input to the particular circuit implemented for the selected polynomial. A data input receives as input the data bits coming in from device FIG. Initially, each latch is cleared to a zero state.
Download Cyclic And Computer Generated Designs
As a data bit is input to the register, a shift occurs from one latch to the next. Once the last bit of a data stream is entered e. The generation of horizontal CRC can occur at data path clock speeds, since simple exclusive OR gates and shift registers are used.
Returning to FIG.
Related Cyclic and Computer Generated Designs
Copyright 2019 - All Right Reserved