Smark Key System for your Home?

Check this out.
www.tokai-rika.co.jp (click on the 'English' button unless you read Japanese)
This company made Toyota's smart key system. There is also a smart-key watch for LS (Lexus) but not for Prius. You can see that the smart key system has been used in door entry as well.

BTW, smart key system does not do code rolling. It is based on encryption technology. If you wish to know more, I can point you to a few technical articles.

Eric

 

<div class='quotetop'>QUOTE(ceric @ Feb 6 2007, 10:29 AM) [snapback]386161[/snapback]</div>

Back in the early days (circa 2004) there were discussions about this and we thought that the smart key did code-rolling. If you have definitive information, I'd be interested to see it, and I'm sure others would as well. I presume the encryption you refer to prevents simple capture-and-repeat as a way to steal the car. Details would be interesting.

 

<div class='quotetop'>QUOTE(daniel @ Feb 6 2007, 03:16 PM) [snapback]386241[/snapback]</div>

http://www.eetimes.com/issue/fp/showArticl...cleID=187002723
It does mention both code hopping and encryption. So I stand corrected.
However, we can never be sure how the Toyota version was implemented.
A longer version can be found thru a link on the page.

 

<div class='quotetop'>QUOTE(ceric @ Feb 6 2007, 02:15 PM) [snapback]386330[/snapback]</div>

Requires registration.

 

<div class='quotetop'>QUOTE(daniel @ Feb 6 2007, 06:32 PM) [snapback]386384[/snapback]</div>

Sorry, I didn't know that.

Auto security apps ride wireless


EE Times
(05/08/2006 10:00 AM EST)

With consumers' demands for safety and security serving as a catalyst for automotive electronics expansion, carmakers are being challenged to implement cost-effective, performance-oriented electronic control modules. Automotive safety and security systems provide a synergistic bridge between the automakers' product-differentiation goals and consumer needs.

Automotive wireless systems are continuing to unfold, from the well-established application of remote keyless entry to emerging ones, such as passive keyless entry, tire pressure monitoring, electronic toll collection and Bluetooth hands-free systems. These wireless connections are instrumental in advancing safety and security modules. The emergence of additional dedicated short-range communication systems for automotive safety and security applications is limited only by the availability of cost-effective technology.

But beyond the constant pressures to reduce time-to-market cycles and increase functionality, designers face a range of challenges, including cost-effective performance enhancements, power consumption, system size and encryption security.

For example, let's examine a wireless system that typifies many of the challenges faced by today's system architect: a smart transponder that can both receive and transmit data. In this bidirectional communication system, the basestation and transponder can communicate automatically, without a human interface. A low-cost, bidirectional communication trans- ponder can be made that uses dual frequencies: 125 kHz for receiving data and UHF (315, 433, 868 or 915 MHz) for transmitting data. The bidirectional communication range is typically less than about 3 meters, due to the nonpropagating nature of the 125-kHz signal. Since the transponder continues to include the pushbuttons for optional operations, it supports long unidirectional range (from the transponder to the basestation) for transmitting pushbutton information.

The basestation transmits commands with a 125-kHz frequency and looks for any responses in UHF from valid transponders in the field. The smart transponder is normally in the receiving mode and looks for any valid 125-kHz basestation commands. The transponder transmits responses with UHF if any valid basestation command is received. This is referred to as a passive-keyless-entry (PKE) system. The PKE system utilizes the 125-kHz circuits for bidirectional communication. A low-cost, space-saving, power-conserving PKE transponder can be made by using an integrated system-on-chip, smart microcontroller that includes both digital and low-frequency analog front-end sections.

As designers gain more system experience, they are challenged to make the PKE transponder reliable enough to serve as a cost-effective replacement for the conventional remote-keyless- entry transponder--all while ensuring that certain system objectives are satisfied. Although the PKE transponder would seem to require complex and expensive circuits, the challenges the designer faces are addressed by use of relatively simple, low-cost circuits that are centered around a smart PIC microcontroller (PIC16F639) that includes all the functions to support secure bidirectional communications.

The smart PKE system shown in the figure still has pushbuttons for optional operations, but the main operation is accomplished without any human interaction. The bidirectional communication sequence is as follows:

• The basestation transmits commands at 125-kHz frequency.

• The transponder receives those commands via the three orthogonally placed 125-kHz LC resonant antennas.

• If the command is valid, the transponder transmits responses (encrypted data) via a UHF transmitter. If the data is correct, the basestation receives the responses and activates switches.

One of the challenges for design engineers is the cost-effective implementation of system performance enhancements, such as communication range, antenna orientation, small packages, encryption security and low power consumption in both "key-on" and "key-off" conditions. Improving the range of the 125-kHz basestation command for reliable operations, as well as maintaining long battery life in the transponder, address key system enhancements.

In battery-powered transponder applications, the maximum communication distance with UHF is about 100 meters, but only a few meters for the low frequency, 125 kHz. Therefore, the communication range of the dual-frequency PKE transponder is limited by the range of the 125-kHz basestation command. The 125-kHz signal falls off very quickly over distance, due to the nonpropagating nature of the low-frequency signal. For example, assuming the base station outputs around 300 Vpp of antenna voltage, the voltage picked up by the transponder's coil antenna at roughly 3 meters away is only about 3 mVpp, which is within a noise level of the application environment. Detecting the weak signal is a challenging performance-oriented issue for system designers.

For increasing the range of the 125-kHz basestation command, two possible solutions should be considered: increasing either the basestation's transmitter power or the transponder's input sensitivity. The transmitter's maximum power is generally defined by government regulations. Therefore, assuming that the basestation is outputting the maximum power within the allowable limits, increasing the input signal-detection sensitivity is the only effective choice. To achieve a 3-meter, bidirectional communication range, the transponder's input sensitivity needs to be about 3 mVpp.

Antenna directionality
Any radio signal radiated from an antenna element propagates with a certain directional angle, and exhibits higher directionality (or narrower radiation angle) when excited by a good antenna. The low-frequency (125-kHz) signal radiated from an LC resonant circuit is not as directional as the high-frequency signal, but it still has directional field components. With the given design conditions of the transponder, the communication range (or induced voltage) of the low-frequency signal is dependent on how well the basestation and the transponder antennas are coupled inductively. The best mutual coupling occurs when the two antennas are oriented face-to-face.

For hands-free PKE applications, the transponder can be placed in any direction inside a person's pocket. Therefore, the best chance that the transponder antenna is faced to the fixed basestation antenna orientation is approximately 30 percent (x, y, z directions). This chance increases to approximately 100 percent if the transponder has three orthogonally placed antennas. In that case, the transponder can pick up the basestation signal at any given direction.

The PIC16F639's operation can be managed effectively for battery power savings. The microcontroller must also operate with minimum circuits during inactive mode. The PIC16F639 in this transponder includes both low-frequency front-end and digital sections. The low-frequency front-end section is consistently searching for input signals, while the digital section is in sleep mode to save battery power and wakes up only when a valid basestation command is received. This can be achieved by using a specific wake-up filter in the front-end section. The low-frequency detection circuit is programmed to make its output available only for the input signal with a predefined header.

Power management, size
In addition to the specific filters, the PIC16F639 features proprietary nanoWatt Technology, which gives the system designer greater control of the on-chip peripherals, including the 8-MHz internal oscillator with several software-selectable speed options down to 32 kHz. The extremely low sleep-current consumption, combined with a fast-startup internal oscillator, supports low-power-consumption design. Periodic wake-up mechanisms include low-power real-time clock operation, ultralow-power wake-up and an extended low-power watchdog timer. With these extensive power-management features, designers are able to implement power saving in the application's software and gain tighter control of overall power consumption at reduced cost.

The degree of integration between the MCU and analog front end was carefully evaluated to ease implementation and flexibility while maintaining a small footprint. A "dual-die in a single package" approach was chosen, which supports future migrations to different MCUs, based on application requirements. The two functional dice are internally bonded via a serial peripheral interface.

The PIC microcontroller family is supported by an extensive range of package options. Devices from six to 80 pins are available. Package options of 20 pins or less are excellent choices for space-constrained applications in wireless access systems. The combination of small form factor, advanced on-chip peripheral integration and cost efficiency offers the system designer a foundation for creating enhanced systems that meet the challenges of wireless system implementation.

The patented KEELOQ global-standard cryptographic technology provides cost-effective authentication, keyless entry and other remote-access control systems. KEELOQ utilizes an industry-proven code-hopping encoding methodology. The code changes when the encoder device is activated, and the code is securely transmitted. With an implementation based on an encoder and decoder pair, the encoder is in the remote, and transmits a rolling-code ID number and counter value.

The decoder is in the receiver and decodes the message sent by the encoder remote. It stores the identification numbers and counter values of the remotes that it has "learned." The decoder allows access only to "learned" remotes.

KEELOQ encryption is a highly secure algorithm achieved by means of a complex equation and randomizer with a 32-bit result. For parking-lot entry applications, a person can drive onto the parking lot without stopping, because the system recognizes the PKE transponder within an active zone of about 3 meters.

The designers of wireless secure-access systems for the vehicles of tomorrow may encounter their share of challenges. Cost-effective microcontrollers offer a proven, reliable building block for wireless systems within the vehicle. The implementation of a low-cost bidirectional communication transponder using an integrated system-on-chip solution is an example of a wireless system that delivers enhanced safety and security functions to the driver. While the PKE transponder receives low-frequency basestation commands and responds with encrypted data via an UHF transmitter, it can operate without any human intervention. A PKE fob transponder located in the driver's pocket can lock or unlock entrance doors automatically, without any human activation.

A longer version of this article can be viewed at www.automotivedesignline.com. Search for article ID: 175002556.

By Youbok Lee (youbok.lee@microchip. com), a technical staff engineer in the Security, Microcontroller and Technology Division, and Willie Fitzgerald, a product marketing director for the Automotive Products Group at Microchip Technology

 

Doesn't this belong under Technical?

Anyhoo we had a lively debate on this topic about a year or so ago. Here are some particulars for various systems

 

<div class='quotetop'>QUOTE(Pinto Girl @ Feb 6 2007, 05:02 PM) [snapback]386435[/snapback]</div>

ceric: The article is interesting, but does not address the Toyota system specifically. As Jayman points out, and as I also said above, we had lengthy discussions about this way back in the early days. I'm not sure anyone really knew for sure exactly how our SKS system operates.

 

Unless Toyota is willing to release such information, all I can do is guess and assume - you know what happens when you nice person/u/me - it functions like the system profiled in the DST Break technical paper, and the TI car transponder rolling code documentation.