Pointers to what an RNGA is?

Hi All,

I've been investigating various (non-DSP, sorry!) processors and have
come across some Freescale parts with an "RNGA" (random number
generator accelerator).  See, for example, 

http://www.freescale.com/files/32bit/doc/white_paper/IMX31SECURITYWP.pdf

http://tinyurl.com/4qgg3r

The most detail I can find is in section 5.5:

"The random bits are generated by clocking ****ft registers with clocks
derived from ring oscillators. The configuration of the ****ft
registers ensures statistically good data, meaning data that looks
random. The oscillators with their unknown frequencies provide the
required entropy needed to create random data."

Does anyone have a pointer to more detail in how these things work?

Any pointers or information appreciated!

Ciao,

Peter K.

PS: Suggestions for other newsgroups to ask the question in also
welcome.

-- 
"And he sees the vision splendid 
of the sunlit plains extended
And at night the wondrous glory of the everlasting stars."