If you rather trust a hardware random number generator you can build and audit yourself, rather than buying some trusted (according to the vendor) platform module, this series may be for you. In this episode I explain how the Zener/avalanche diode based noise generator I use works.
Table of Contents
- 00:00:00
- Randy Bush’s lightning talk at RIPE-68 on the the Cryptech project
- 00:01:05
- Why another hardware random number generator (HWRNG)?
- 00:01:40
- My talk on the limits of cryptography at the 2014 Easterhegg in Stuttgart/Germany. (Don’t let yourselves get deterred by myself being introduced in German, the talk is in English.)
- 00:02:20
- End user auditability as the ultimate goal
- 00:03:20
- Auditable and general purpose components
- 00:04:15
- Diversity as a goal
- 00:05:00
- Full disclosure architecture and design
- 00:05:36
- Why random number generators can’t be blackbox-tested
- 00:07:00
- Tamper resistant ( and “tamper proof”) hardware random number generators vs. auditability
- 00:08:08
- Possible but not so practical random sources
- 00:10:43
- The avalanche effect in semiconductor junctions
- 00:11:22
- Zener/avalanche diodes
- 00:13:28
- The hardware components it takes…
- 00:15:09
- My current (pre-)prototype
- 00:18:25
- How I got here: Failures and design decisions
- 00:30:42
- Looking at the circuit with an oscilloscope
- 00:31:48
- My current noise generater circuit
- 00:34:45
- Comparing first and second stage output
- 00:36:05
- A call for support
To make the second transistor get out of saturation faster (and possibly making a BC547 or 237 suitable), you can borrow the trick that made the 74LSxx series much faster than the 74xx series.
LS stands for low power schottky. What they did was add a schottky diode with anode on the base, cathode on the collector.
When you then give the transistor base current, instead of the transistor going into saturation, then, when the collector drops to about 0.4V (the base is at 0.66, the schottky forward voltage higher), the schottky steals the base current, and the transistor does not go into saturation.
It works exactly the same as without the schottky, only without the saturation recovery time.
You want a small signal schottky, like a bas85/bat85 or smaller.
Can you make a tiny white noise generator with earplug and volume control?
Hi Richard,
white noise for acoustic purposes has little to do with the crypto grade output of the generator here; I assume it is possible to do something like you want (I assume it is to deal with a tinnitus?) but the real problem with that sort of issue is with the size and power consumption.
If you want an in-ear solution this is really tricky. If on the other hand you want something with a form factor similar to an MP3 player, then actually just recording white noise (you can get that from an old, analog TV set if nothing else) and putting that on an MP3 player should actually do the trick quite nicely.
Cheers,
Benedikt