Hsbx HardwareRNG

Contents 
[edit] Why
 Generate Cryptostrong randomness and feed /dev/hw_random (or other things)
via USB makes collide :
 electronics
 software
 crypto goodness
 Multiple designs are available online, want to compare randomness quality
 Have a bunch of tiny45 i want to find a use for
 Because i can (try)...
[edit] What
some transistors, some caps, attiny45
[edit] How
[edit] Where am i ?
ATM @ Jege home, beeing tested
[edit] Grumbles, Notes
v1 generation is "a bit" biased : ent :
Entropy = 7.977742 bits per byte. Optimum compression would reduce the size of this 2355200 byte file by 0 percent. Chi square distribution for 2355200 samples is 62743.07, and randomly would exceed this value 0.01 percent of the times. Arithmetic mean value of data bytes is 134.1802 (127.5 = random). Monte Carlo value for Pi is 3.000950239 (error 4.48 percent). Serial correlation coefficient is 0.000289 (totally uncorrelated = 0.0).
exceed this value 0.01 percent of the times > Completely unfit for crypto purposes...
exemple for /dev/urandom :
Entropy = 7.999995 bits per byte. Optimum compression would reduce the size of this 31457280 byte file by 0 percent. Chi square distribution for 31457280 samples is 232.09, and randomly would exceed this value 75.00 percent of the times. Arithmetic mean value of data bytes is 127.5220 (127.5 = random). Monte Carlo value for Pi is 3.139891052 (error 0.05 percent). Serial correlation coefficient is 0.000201 (totally uncorrelated = 0.0).
i suspect the output from the sn74als04an (0 > vcc2) to weirdly interract with the binary reading on the tiny45 (0 if(v<0.3*vcc), 1 if(v>0.6*vcc), "random" otherwise, vcc =5) 5*.6 = 3v which is the peak value to ensure the reading of a 1. Non vonneuman* decorrelated reading from the tiny read a LOT of 0s...
i'll try to think about a v2 that outputs a 05v square signal. (will try something along the line of the jfet link, eliminates the sn74 for another 3904, seems the output should be 04.5v)
if the output is still biased maybe some shielding... wish i had more of those in stock already...
 to read 1 decorrelated byte :
result = 0; for(i=0;i<8;){ do{ oldreadc= (PINB & _BV(LED0_BIT)); readc = (PINB & _BV(LED0_BIT)); }while(oldreadc ^ readc == 0); result = readc << i; i++; }
[edit] Online resources
 http://www.kernel.org/doc/Documentation/hw_random.txt
 http://www.cryogenius.com/hardware/rng/
 http://web.jfet.org/hwrng.html
 http://www.obdev.at/products/vusb/
 http://codeandlife.com/2012/02/22/vusbwithattiny45attiny85withoutacrystal/
 http://imotp.sourceforge.net/noise.pdf
Darn, the idea was in the air it seems... well, will learn more with the desing presented here...