Black hat Black hat A black hat hacker (or black-hat hacker) is a hacker who "violates computer security for little reason beyond maliciousness or for personal gain". The term's origin is often attributed to hacker culture theorist Richard Stallman (though he denies coining it) to contrast the exploitative hacker with the white hat hacker who hacks protectively by drawing attention to vulnerabilities in computer systems that require repair. The black hat/white hat terminology originates in the Western genre of popular American culture, in which black and white hats denote villainous and heroic cowboys respectively. Black hat hackers are the stereotypical illegal hacking
Cyclic prefix 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 in