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Four Processors Provide Communication/Storage Security

Data security is all important for financial systems, medical records, and energy infrastructure control systems – to name a few applications. A number of standard security algorithms are available in MCUs, but AES is the mainstay.

The Advanced Encryption Standard (AES) symmetric-key encryption standard is used by the U.S. government. The National Institute of Standards and Technology held a contest to initiate the development of encryption algorithms that would replace DES. AES was announced on November 26, 2001, after a five-year standardization process in which 15 competing designs were presented and evaluated.

Another type of security is the SHA series of secure hash algorithms that do not encrypt, but are used to check that a file has not been changed (corrupted) during transfer or storage. The Freescale Semiconductor K60 32-bit MCU family has a 100-MHz ARM Cortex-M4 core and includes hardware encryption supporting AES, and SHA-256 algorithms. The device also features Ethernet with IEEE 1588, high-speed USB 2.0 On-The-Go, and tamper detection capabilities. Devices start from 256 Kbytes of flash in 100LQFP packages, extending up to 1 Mbyte in a 256MAPBGA package. The chip has ten low-power modes with power and clock gating for optimal peripheral activity and stop currents of <500 nA, run currents of <200 uA/MHz, plus 4-µs wake-up time from stop. It runs from 1.7 to 3.6 V and has a 16-bit SAR A/D converter with PGA and a 12-bit D/A. Cost is around $5.60 in hundred quantities.

Another secure candidate is Texas Instruments’ low-power, low cost CC430F5133, which is an SoC with a 16-bit MSP430 processor and an RF core. It features a 128-bit AES security encryption/decryption coprocessor. The CPU portion of this device uses only 5 mA max at 20 MHz and 2 µA in standby. The RF transciever works at 300 to 348 MHz, 389 to 464 MHz, and 779 to 928 MHz. The radio in RX takes 15 mA at 250 kbits/s and 915 MHz. The chip costs about $6 and has lots of other features like a 12-bit A/D converter with internal reference, sample-and-hold, and autoscan, a 32-bit hardware multiplier, a three-channel DMA, and a hardware real-time clock. It has 8 kbytes of flash and 2 kbytes of RAM. Larger, 32-Kbyte flash versions are available.

Atmel has the AVR UC3 A3 series, available with an optional AES crypto module capable of 128 to 256-bit AES encryption at speeds of up to 22.8 Mbytes/s. The MCU also has Hi-Speed USB On-The-Go, SD/SDIO card, and NAND flash with ECC and SDRAM interfaces. The chip features a multilayered databus, 128 Kbytes of SRAM, and a multichannel peripheral and memory-to-memory DMA controller. The device also features a Hi-Fi stereo audio D/A and a full duplex multichannel I2S audio interface.

The MAXQ1004 MCU from Maxim Integrated Products includes an AES encryption engine, a 10-bit A/D converter, a 1-Wire slave interface, SPI, a random-number generator, a temperature sensor, and a 16-bit pipelined CPU. Performance bandwidth is sufficient to handle master or slave challenge-response authentication in portable devices. The device runs from 1.7 to 3.6 V and has 16 Kbytes of flash and 640 bytes of RAM. Factory programming of a secret key is available. The chips AES engine is a block cipher supporting encryption and decryption and operates independently of the processor, except for setting up an operation through the AES control register.