Grey hat Grey hat The term "grey hat", alternatively spelled as "greyhat" or "gray hat", refers to a computer hacker or computer security expert who may sometimes violate laws or typical ethical standards, but does not have the malicious intent typical of a black hat hacker. The term began to be used in the late 1990s, derived from the concepts of "white hat" and "black hat" hackers. When a white hat hacker discovers a vulnerability, they will exploit it only with permission and not divulge its existence until it has been fixed, whereas the black hat will illegally exploit it and/or tell
Cyclic prefix formula_17. Cyclic prefix In telecommunications, the term cyclic prefix refers to the prefixing of a symbol, with a repetition of the end. The receiver is typically configured to discard the cyclic prefix samples, but the cyclic prefix serves two purposes: For the cyclic prefix to serve its objectives, it must have a length at least equal to the length of the multipath channel. The concept of a cyclic prefix is traditionally associated with OFDM systems, however the cyclic prefix is now also used in single carrier systems to improve the robustness to multipath propagation. A cyclic prefix is often used