MCS3142_14 datasheet(5/37 Pages) MICROCHIP

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 2014 Microchip Technology Inc.

DS40001747A-page 5

MCS3142

Most low-end keyless entry transmitters are given a

fixed identification code that is transmitted every time a

button is pushed. The number of unique identification

codes in a low-end system is usually a relatively small

number. These shortcomings provide an opportunity

for a sophisticated thief to create a device that ‘grabs’

a transmission and retransmits it later, or a device that

quickly ‘scans’ all possible identification codes until the

correct one is found.

MCS3142, on the other hand, employs both the Classic

and Ultimate KEELOQ code hopping technology. The

high-security level of MCS3142 is based on the

patented KEELOQ technology.

For Classic KEELOQ technology, a block cipher based

on a block length of 32 bits and a key length of 64 bits

is used. The algorithm obscures the information in such

a way that if a single hopping code data bit changes

(before encryption), statistically more than 50% of the

encrypted data bits will change.

Ultimate KEELOQ technology uses the industry

standard AES-128 encryption algorithm to obscure

data using 128 bits for both its block and key length. In

addition to the security of Classic KEELOQ technology,

Ultimate KEELOQ technology sends a time-stamp as

part of the transmission. This can prevent other more

sophisticated attacks such as the ‘jam-and-relay’

attack.

MCS3142 데이터시트(PDF) 5 Page - Microchip Technology