Tag Archives: AT88SC102

Securing offline passwords with Atmel MCUs

Over the past few months, Bits & Pieces has featured a number of DIY offline password keepers built around Atmel microcontrollers (MCUs).

First up is the official HackADay Mooltipass. Powered by Atmel’s ATmega32U4, the device is equipped with an easily readable screen, a read-protected smart-card (AT88SC102) and flash memory to store encrypted passwords.

Next up is the USBPass. Designed by a Maker named Josh, the platform comprises an ATmega32U2 MCU, USB connector, three buttons and a few passives chips. Like the Mooltipass, the USBPass is connected to a computer via USB and read as an HID keyboard.

The latest Atmel-powered offline password keeper to surface in the Maker community and on the HackADay website? Cyberstalker’s ATMega32U4-packing Final Key, which includes a single button and LED, all neatly enclosed in a 3D printed case.

According to HackADay’s Mathieu Stephan, the Final Key is linked to the host computer via USB and recognized as a composite comm device/HID keyboard, requiring Windows-based devices to install drivers.

“AES-256 encrypted passwords are stored on the device and can only be accessed once the button has been pressed and the correct 256 bit password has been presented through the command line interface,” Stephan explained. “Credentials management and access are also [executed by] the latter.”

Interested in learning more about the ATMega32U4-powered Final Key? You can check out the project’s official page here.

Atmel powers HackADay’s (offline) Password Keeper

The HackADay crew has chosen Atmel’s ATmega 32U4 microcontroller (MCU) to power its offline password keeper. Known as “Mooltipass,” the platform is also equipped with an easily readable screen, a read-protected smart-card (AT88SC102) and flash memory to store encrypted passwords.

Atmel’s ATmega 32U4 is the same microcontroller [found] in the Arduino Leonardo, allowing us to use the numerous libraries that have been developed for it. In the final schematics, we’ll add an expansion connector so users may connect additional peripherals (we may switch to a FOUR4 layers PCB at this point),” explained HackADay’s Mathieu Stephan. “The microcontroller’s USB lines are protected from ESD by the IP4234CZ6. For encrypted password storage, we found the cheap 1Mbit AT45DB011D FLASH which also has 2/4/16Mbits pin compatible versions. If our beta testers find that 1Mbit is not enough, upgrading the Mooltipass would be easy.”

As noted above, Atmel’s AT88SC102 was chosen to be the secure smart-card, which offers 1024bits read/write protected EEPROM. In terms of the display, Stephan says the team has temporarily opted for the OLED screen shown in the picture above, although the creation of another mooltipass version with an IPS LCD is more than likely.

“These components choices made the voltages electronics fairly simple. The whole solution is powered by the ~5V coming from the USB, and the ~3.3V required by both the flash and the display is provided by the ATmega32U4 internal LDO regulator (~55mA @ 3.0 to 3.6V),” Stephan continued.

“The +12V also needed by the display is generated by a $1 regulated charge pump DC-DC converter. If we had to use a conventional step-up, the component count (and cost) would be much higher. Notice that we put a P-MOSFET in series with the latter as the output voltage when the DC-DC is not working is not 0V but VCC (here +5V). We also used another P-MOSFET to switch the power supply going to the smart card.”

In addition, the HackADay crew selected two resistor networks R6&R7 as voltage dividers to transform 5V signals to 3.3V.

“Fortunately, the ATmega32U4 can receive LVTTL signals, so we don’t need level shifters to get the data coming from the 3.3v-powered flash memory,” he added.

Interested in learning more about the Atmel-powered Mooltipass? You can check out the project’s official dedicated Google Group page here.