Good quality entropy sources are indispensable in most modern cryptographic
protocols. Unfortunately, many currently deployed networked devices do not
include them and may be vulnerable to Random Number Generator (RNG) attacks.
Since most of these systems allow firmware upgrades and have serial
communication facilities, the potential for retrofitting them with secure
hardware-based entropy sources exists. To this aim, very low-cost, robust, easy
to deploy solutions are required. Here, a retrofittable, sub 10$ entropy source
based on chaotic dynamics is illustrated, capable of a 32 kbit/s rate or more
and offering multiple serial communication options including USB, I2C, SPI or
USART. Operation is based on a loop built around the Analog to Digital
Converter (ADC) hosted on a standard microcontroller.Comment: 4 pages, 6 figures. Pre-print from conference proceedings; IEEE 21th
International Conference on Electronics, Circuits, and Systems (ICECS 2014),
pp. 175-178, Dec. 201
