Se­cu­rity Blan­ket

Kevin utilised rock-solid pro­tec­tion for his games

Retro Gamer - - IN THE CHAIR: KEVIN EDWARDS -

matt God­bolt cre­ated Javascript em­u­la­tor js­beeb, and get­ting games pro­tected by

Kevin to run on it was a chal­lenge. Matt says, “Tim­ings are in­cred­i­bly im­por­tant for ac­cu­rate em­u­la­tion. Games pro­gram­mers would take ad­van­tage of tim­ing sub­tleties and un­doc­u­mented side-ef­fects of in­struc­tions. Anti-copy mech­a­nisms were of­ten the most sen­si­tive to this. The 6502 CPU in the BBC

Mi­cro had a num­ber of bugs too – [some] game pro­tec­tion sys­tems would use this to their ad­van­tage to try and pre­vent re­verseengi­neer­ing of their code bases. Kevin Ed­wards’ pro­tec­tion was the undis­puted king – us­ing in­ter­rupt tim­ings, var­i­ous hard­ware timers and even the self-mod­i­fy­ing de­cryp­tion code it­self to gen­er­ate the keys to de­crypt the game.”

James Bon­field, renowned BBC hacker, talks about Kevin’s pro­tec­tion on Ex­ile. “Kevin was the king of copy­right pro­tec­tion and the only game au­thor that truly de­feated all my at­tempts. He had the bright idea of en­crypt­ing us­ing the 1MHZ hard­ware timer val­ues, the code do­ing the en­cryp­tion, and the pro­gram counter. This means that the code can­not be mod­i­fied, it can­not be moved (it is po­si­tion-de­pen­dent) and it can­not be eas­ily sim­u­lated due to the real-time na­ture of the hard­ware clocks. Truly a ge­nius.”

The Ul­ti­mate BBC games, con­verted by Paul Proc­tor and with tape pro­tec­tion by Kevin.

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