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A rolling code (or sometimes called a hopping code) is used in keyless entry systems to prevent replay attacks, where an eavesdropper records the transmission and replays it at a later time to cause the receiver to 'unlock'. Such systems are typical in garage door openers and keyless car entry systems. == Techniques == * Common PRNG (pseudorandom number generator) — preferably cryptographically secure — in both transmitter and receiver * Transmitter sends 'next' code in sequence * Receiver compares 'next' to its calculated 'next' code. * A typical implementation compares within the next 256 codes in case receiver missed some transmitted keypresses. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Rolling code」の詳細全文を読む スポンサード リンク
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