Si4010-Keyfob-AES-DEMO
Si4010 K
EY
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AES C
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1. Purpose
Thank you for your interest in Silicon Laboratories’ Si4010 SoC RF key fob demo kit with AES capability. The
Silicon Laboratories Si4010 key fob demo kit with AES capability contains everything you need to familiarize
yourself with and evaluate the Si4010 RF SoC. The kit has two versions, one for the 434 MHz band and one for the
868 MHz band. The key features of the development platform are as follows:
The key fob demo board has five push buttons and one LED output, a PCB antenna, and a battery in a plastic
case.
The key fob uses hardware-accelerated 128-bit advanced encryption standard (AES) encryption and rolling
counter for RKE application.
The receiver demo board has a graphic LCD to display received key fob commands.
The provided software pack contains all the documentation and files needed to develop a user application. The
kit supports the use of Silicon Laboratories’ Integrated Development Environment (IDE) for software debugging
and the use of the Keil C compiler, assembler, and linker toolchain.
Contains demo applications using API functions and the key fob demo application.
2. Kit Contents
The kit contains the following items:
Qty
Part Number
4010-DAAKF_434
1
1
1
1
1
1
4010-DAPB_434
4313-DACB_ANY
MSC-AT50-434
MSC-PLPB_1
CRD2032
MSC-DKSW1
4010-DAAKF_868
1
1
1
1
1
1
4010-DAPB_868
4313-DACB_ANY
MSC-AT50-868
MSC-PLPB_2
CRD2032
MSC-DKSW1
Description
Si4010 Key Fob Demo Kit with AES Capability 434 MHz
Si4010 Universal Key Fob 434 MHz
Si4313 LCD FSK/OOK Receiver any band
434 MHz Antenna
Key Fob Plastic Case (translucent grey)
CR2032 3 V coin battery
Wireless Development Suite disc
Si4010 Key Fob Demo Kit with AES Capability 868 MHz
Si4010 Universal Key Fob 868 MHz
Si4313 LCD FSK/OOK Receiver any band
868 MHz Antenna
Key Fob Plastic Case (translucent red)
CR2032 3 V coin battery
Wireless Development Suite disc
Rev 1.1 4/11
Copyright © 2011 by Silicon Laboratories
Si4010-Keyfob-AES-DEMO
Si4010-Keyfob-AES-DEMO
Figure 1. Si4010 Universal Key Fob and Plastic Case (P/N 4010-DAPB 868 and MSC-PLPB_1)
Figure 2. Si4313 LCD FSK/OOK Receiver Any-Band (P/N 4313-DACB ANY) with 434 MHz Antenna
(P/N MSC-AT50-434)
2
Rev 1.1
Si4010-Keyfob-AES-DEMO
3. Key Fob Demo with AES Capability
The 4010-DAPB RKE key fob transmitter and the Si4313 FSK receiver are the transmit and receive devices used
in this key fob demo. This transmit/receive pair can be used to evaluate the capabilities of the Si4010 transmitter
and the Si4313 receiver.
3.1. Operation of the Demo
The Si4313 demo receiver board uses the following RF parameters:
9.6 kbps
FSK modulation
433.92 MHz or 868.3 MHz center frequency (menu selectable)
±70 kHz deviation
If any push button is pressed on the key fob, it sends a message to the receiver. The demo uses Silicon Labs'
general EZMacPRO protocol.
Table 1. General EZMacPRO Extended Packet Configuration Used by Demo Key Fobs
Preamble
Min.13 bytes
0xAA...0xAA
Synch Word
2 bytes
0x2DD4
CTRL
MAC Header
5 bytes
CID
SID
DID
PL
MAC Payload
0...64 bytes
NHDR
NWK payload
CRC
2 bytes
CRC
3.2. Association
To enable the receiver to react to the button presses on the key fob(s), they have to be paired (i.e., the key fob has
to be associated to the receiver by pressing the left and right buttons simultaneously on the key fob).
Table 2. The MAC Payload Field of the “Associate Request from TX only Device” Packet
MAC Payload
NHDR
1 byte
0x47
NWK Payload
1 bytes
0x05
1 byte
0x01
1 byte
AES
4 byte
Address
4 byte
Rolling Counter
3.2.1. Meanings of the Different Fields
AES—Defines
whether the transmitter is using AES-128 encryption or not. It is set to 0x01; then, the Rolling
counter field of the packets is extended to 16 bytes length (12 dummy bytes are appended) and is encoded by
AES-128. Other fields of the packet are not affected by the encryption.
Address—4
bytes of key fob address. The four byte random number factory burned in the Si4010 is used as
the address.
Rolling Counter—The
transmitter increments a 4 byte counter after every packet transmission. This counter is
stored in the MTP memory of the Si4010.
If the receiver accepts the association, it registers the Address, Master Key, and Rolling Counter value of the
requesting key fob.
The Master accepts the association if it is in pairing mode and there is a free slot for a key fob (i.e., if there are
fewer than four key fobs associated to the receiver).
After power up, the Receiver board is in pairing mode automatically. After pairing, it goes to normal packet
reception mode. The Pairing mode can be invoked by pressing the push button, PB3, on the Receiver Board. This
button needs to be pressed before the second and any subsequent pairing. If the PB is pressed for more than one
second, the receiver disassociates all key fobs.
Rev 1.1
3
Si4010-Keyfob-AES-DEMO
3.3. Button is Pressed on the Key Fob
If any single button or button combination (except association combination) is pressed on the key fob, then it
transmits a key fob data packet showing the button number in the button field.
Table 3. The MAC Payload Field of the “Key Fob Data” Packet
MAC Payload
NHDR
1 byte
0x04
NWK payload
1 byte
AES
4 bytes
Address
1 byte
Button
2 bytes
TEMP
1 byte
Battery
4 byte
Rolling Counter
3.3.1. Meaning of the Different Fields
AES—Defines
whether the transmitter is using AES-128 encryption. It is set to 0x01, then Button, Temp,
Battery, and Rolling counter fields of the packets are extended to 16 bytes length all together and are encoded
by AES-128. Other fields of the packet are not affected by the encryption.
Address—4
bytes of key fob address. The four-byte random number factory burned in the Si4010 is used as
the address.
Button—Each
bit of this byte corresponds to the status of a push button on the key fob. If the bit is set, the
given button is pressed. If the bit is cleared, the button is released.
TEMP—The
temperature is encoded as a signed 16-bit integer. Each incremental bit of temperature reading
represents 0.1 °C. If the temperature function is not implemented in the key fob, this field is set to 0xFFFF.
Battery—1
byte unsigned char showing the actual power supply status of the key fob. It must be interpreted as
follows:
1 bit
Lbd Available
1 bit
LBD Status
1 bit
Battery Voltage Available
5 bits
Battery Voltage[4:0]
LBD Available Bit—If
set, the LBD status bit shows the actual status of the battery.
LBD Status—Shows
whether the actual battery voltage is above the LBD limit (set if the actual voltage is below
the threshold). The LBD limit is configurable in the key fob program.
Battery Voltage Available—If
set, the battery voltage information is available.
Battery Voltage—It
shows the actual battery voltage of the key fob. Each increment of the battery voltage bit
corresponds to 50 mV. However, 0 represents 1.7 V.
Rolling Counter—The
transmitter increments a 4 byte counter after every packet transmission. This counter is
stored in the MTP memory of the Si4010.
Since AES is used by the key fob, the receiver board decrypts the encrypted portion of the packet and discards the
dummy bytes. Then, the receiver board checks the sync counter value against its own copy of the sender key fob's
counter. If the key fob sync counter value minus the copy counter value is more than zero and less than a
configurable window value (default value is 10), the master increments the copy.
4
Rev 1.1
Si4010-Keyfob-AES-DEMO
3.4. Key Handling
Application
Level
RKE_MK
Function
Level
AES_128
Node_Association
AES_128
Node_ButtonPress
AES_128
Functionzzzzzzzz
Assoc_K
Btn_K
FuncX_K
Session
Level
AES_128
12byte padding(0) +
Node Addr
AES_128
12byte padding(0) +
Node Addr
Assoc_SK
Btn_SK
MK:
SK:
Master Key
Session Key
Figure 3. SRW AES128 Applications Key Hierarchy
AES keys used in the demos are generated according to the hierarchy shown in Figure 3. Only the Application
level keys are stored on the receiver board. The function level keys are calculated at power-up. The Session level
keys are calculated at their first use.
In the key fobs Function level, keys are not generated but only stored to save power. The Session level keys are
calculated at each power up.
The Assoc_SK is used for association packets, and the Btn_SK is used for encrypting the messages generated by
a button press.
3.5. Key Fob Firmware Description
The complete project of the program used in the demo key fob can be found in the Si4010 documentation kit in the
“rke_demo” folder.
The key fob wakes up for button push or battery insert. If the battery was inserted, the vSys_FirstPowerUp() API
function is called, which shuts down the chip after 600 ms. This is for safe startup in case of battery contact
bouncing. Upon button push wakeup, the system variables and hardware control registers are initialized first, and
the session keys used in the AES encoding are generated from the function keys and the device address. Then,
button debouncing is made.
If a valid button push is detected, first a packet is assembled and transmitted six times for the LED receiver demo
board used in the Si4010 Simplified Key Fob Demo Kit (see details in “AN516: Si4010 Simplified Key Fob Demo
Quick Start Guide”). Then, a packet is assembled according to the description in the previous chapters. It is
transmitted in FSK modulation for the Si4313 receiver board (part of this kit), and then also in OOK modulation.
The next step is to increment the sync counter stored in the MTP memory.
If there is no valid button push detected for 3.2 s, the program shuts down the chip.
Rev 1.1
5
微控制器 MCU
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