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TB001

更新时间： 2024-10-30 03:28:59

品牌	Logo	应用领域
美国微芯 - MICROCHIP		/
页数	文件大小	规格书
17页	158K
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USING KEELOQ㈢ TO GENERATE HOPPING PASSWORDS

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TB001 数据手册

AN665

Using KEELOQ to Generate Hopping Passwords

THE “HOPPING” ADVANTAGE

Author:

Lucio Di Jasio

Arizona Microchip Technology, Italy

Password-based access control systems are very pop-

ular today, but the level of security they provide are

often overestimated. Being basically a unidirectional

transmission, a password-based system has two very

important shortcomings which can lead to unautho-

rized access: the code is ﬁxed, and the number of pos-

sible combinations is relatively low.

INTRODUCTION

The purpose of this application note is to demonstrate

how KEELOQ code hopping technology can be conve-

niently employed to implement an automatic code hop-

ping password generator/keypad. Using a PIC12C508,

the hopping code produced by an HCS300 is converted

to a string of 16 hex digits. This string is then trans-

ferred to the PC via the keyboard line, thereby emulat-

ing the actual pressure of a sequence of keys on a

The growing speed of communication lines and the

computing power of available systems increases the

chance of a brute force attack or “code scanning.” The

use of unsecure means of transmission, where code

“grabbing” is possible (i.e., a typical modem connection

over phone lines), can make the use of a ﬁxed code

highly undesirable. Note that these are the same situa-

tion that led to the introduction of the “code hopping”

concept in the remote control market.

standard PC/AT keyboard. Since this conversion pro-

cess is transparent to any application, it appears as if

the user is simply typing on a PC/AT-type keyboard.

An ideal situation for implementing this application

would be in creating a “super password” for general,

access-control secure logins when transmitting infor-

mation onto the internet (i.e., through a browser) or a

Java applet.

The basic idea is to have the access code change each

time it is used through a sequence where the new

codes cannot be predicted even knowing a very large

number of previously used ones. Producing such a

sequence requires the use of a solid encryption engine.

Microchip Technology is currently offering a broad

range of encoders based on the proprietary KEELOQ

code hopping technology. These encoders make pro-

ducing a code hopping remote control easy, but as we

will see, can also be conveniently used to add the hop-

ping advantage to old password based access control

systems in a transparent way.

FIGURE 1: HCS300 AND PIC12C508 PINOUT DIAGRAMS

HCS300

PIC12C508

VSS

VDD

LED

PWM

VSS

VDD

GP5/OSC1/CLKIN

GP4/OSC2

GP0

GP1

GP3/MCLR/VPP

GP2/T0CKI

KEELOQ is a registered trademark of Microchip Technology, Inc.

Microchip’s Secure Data Products are covered by some or all of the following patents:

Code hopping encoder patents issued in Europe, U.S.A., and R.S.A. — U.S.A.: 5,517,187; Europe: 0459781; R.S.A.: ZA93/4726

Secure learning patents issued in the U.S.A. and R.S.A. — U.S.A.: 5,686,904; R.S.A.: 95/5429

IBM PC-AT, IBM and AT are registered trademarks of International Business Machines Corporation

ã 1997 Microchip Technology Inc.

DS00665A-page 1

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与TB001相关器件

型号	品牌	获取价格	描述	数据表
TB001-500	CUI	获取价格	TERMINAL BLOCK
TB001-500-12BE	CUI	获取价格	Terminal and Terminal Block
TB001-500-13BK	CUI	获取价格	Terminal and Terminal Block
TB001-500-13GY	CUI	获取价格	Terminal and Terminal Block
TB001-500-13OR	CUI	获取价格	Terminal and Terminal Block
TB002-500	CUI	获取价格	TERMINAL BLOCK
TB002V-500	CUI	获取价格	TERMINAL BLOCK
TB003	MICROCHIP	获取价格	An Introduction to KELLOQ㈢ Code Hopping
TB003-500	CUI	获取价格	TERMINAL BLOCK
TB003V-500	CUI	获取价格	TERMINAL BLOCK

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