HCS300-IP Microchip Technology, HCS300-IP Datasheet - Page 2

• Manufacturer Part Number: HCS300-IP
• Description: KEE LOQ Code Hopping Encoder
• Manufacturer: Microchip Technology

HCS300
The HCS300 operates over a wide voltage range of
2.0V to 6.3V and has four button inputs in an 8-pin
configuration. This allows the system designer the
freedom to utilize up to 15 functions. The only
components required for device operation are the but-
tons and RF circuitry, allowing a very low system cost.
1.0
Key Terms
• Manufacturer’s code - a 64-bit word, unique to
• Encryption Key - a unique 64-bit key generated
1.1
The HCS product family facilitates several learn strate-
gies to be implemented on the decoder. The following
are examples of what can be done. It must be pointed
out that their exists some third-party patents on learn-
ing strategies and implementation.
1.1.1
The receiver uses the same information that is transmit-
ted during normal operation to derive the transmitter’s
secret key, decrypt the discrimination value and the
synchronization counter.
1.1.2
The transmitter is activated through a special button
combination to transmit a stored 48-bit value (random
seed) that can be used for key generation or be part of
the key. Transmission of the random seed can be dis-
abled after learning is completed.
The HCS300 is a code hopping encoder device that is
designed specifically for keyless entry systems,
primarily for vehicles and home garage door openers. It
is meant to be a cost-effective, yet secure solution to
FIGURE 1-1:
DS21137D-page 2
each manufacturer, used to produce a unique
encryption key in each transmitter (encoder).
and programmed into the encoder during the
manufacturing process. The encryption key
controls the encryption algorithm and is stored in
EEPROM on the encoder device.
SYSTEM OVERVIEW
Learn
NORMAL LEARN
SECURE LEARN*
Manufacturer’s
Code
CREATION AND STORAGE OF ENCRYPTION KEY DURING PRODUCTION
Serial Number or
Transmitter
Generation
Algorithm
Seed
Key
Preliminary
Encryption
such systems. The encoder portion of a keyless entry
system is meant to be held by the user and operated to
gain access to a vehicle or restricted area. The
HCS300 requires very few external components
(Figure 2-1).
Most keyless entry systems transmit the same code
from a transmitter every time a button is pushed. The
relative number of code combinations for a low end sys-
tem is also a relatively small number. These
shortcomings provide the means for a sophisticated
thief to create a device that ‘grabs’ a transmission and
re-transmits it later or a device that scans all possible
combinations until the correct one is found.
The HCS300 employs the K
nology and an encryption algorithm to achieve a high
level of security. Code hopping is a method by which
the code transmitted from the transmitter to the receiver
is different every time a button is pushed. This method,
coupled with a transmission length of 66 bits, virtually
eliminates the use of code ‘grabbing’ or code
‘scanning’.
As indicated in the block diagram on page one, the
HCS300 has a small EEPROM array which must be
loaded with several parameters before use. The most
important of these values are:
• A 28-bit serial number which is meant to be
• An encryption key that is generated at the time of
• A 16-bit synchronization value
The serial number for each transmitter is programmed
by the manufacturer at the time of production. The
generation of the encryption key is done using a key
generation algorithm (Figure 1-1). Typically, inputs to
the key generation algorithm are the serial number of
the transmitter and a 64-bit manufacturer’s code. The
manufacturer’s code is chosen by the system
manufacturer and must be carefully controlled. The
manufacturer’s code is a pivotal part of the overall
system security.
Key
unique for every encoder
production
HCS300 EEPROM Array
Serial Number
Encryption Key
Sync Counter
1996 Microchip Technology Inc.
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code hopping tech-