Microchip Technology PRO MATE II, Руководство пользователя

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PRO MATE
®
II Device Support
DS30243H-page 22

1999 Microchip Technology Inc.
Figure 3.4: K
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Key Generation
3.5 Manufacturer’s Code
When an HCS product is selected as the device to be programmed by the
PRO MATE II programmer, the Enter Key dialog box is displayed when
Program is pressed. As mentioned in Section 3.4, the manufacturer’s code is
very important to prevent cloning of transmitters and should be carefully
guarded. To ensure that the manufacturer’s code remains secret two trusted
people, key custodians, should be given a 20-digit number each. This
prevents the entire manufacturer’s code being entrusted to a single person.
The two custodian keys are XORed to form the manufacturer’s code.
3.5.1 Entering the Manufacturer’s Code
Each of two key custodians are required to enter their custodian key an HCS
part is first selected. The two custodian keys, if entered correctly, are used to
generate the manufacturer’s code. The first 16 digits entered by each
custodian are used to generate the manufacturer’s code, while the last 4 digits
are a checksum. The checksum digits prevent the custodian from entering an
incorrect manufacturer’s code as this directly influences the encryption keys
that are generated. If the checksum entered does not match the key entered,
the custodian will be asked to re-enter the key.
It is only possible to enter the manufacturer’s code once during each session,
when Program is first selected. This prevents the manufacturer’s code being
inadvertently changed during a programming session.
3.5.2 Calculating Custodian Key Checksum
The user should enter the 16-digit portion used to calculate the
manufacturer’s code and press the Calculate Checksum button. This will
allow the program to generate a checksum for the user. The checksum will be
calculated and the complete 20-digit custodian key displayed on the screen.
The key should be written down and stored securely.
Manufacturer’s Code
Seed • XOR
Encryption Key
Serial Number
Source
Algorithm
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Key Generation