NC Scout has posted an article at his Brushbeater blog from one of his readers about how to generate true random numbers (as opposed to pseudo-random numbers and non-random numbers) for one time pad (OTP) encryption – R-Pi OTP/DRYAD True Hardware RNG How-To. It is lengthy and technical, but does a pretty good job of walking you through setting it up on a Raspberry Pi computer.
There are only three ways that I know of to generate a truly random One Time Pad – for the “regular guy”: 1) The old-fashioned way with a set of dice (preferably 10-sided) and paper/pencil; 2) purchase one of AmRRON’s ADL-1 units from AmRRON.com (https://amrron.com/2018/03/18/amrron-dark-labs-otp); 3) The following method outlined in this how-to. Maybe there are others. I wanted to come up with a way for anybody to put one together with easily available components. So here it is. You shouldn’t need to procure any unobtainium to build it. (It was valid in May 2018 when I first put this together. It should be fine as Raspbian Stretch is still the current distribution.)
The script will print either numerical or alphabetic OTPs. Besides the standard OTP generating scripts, also included is a script for generating a DRYAD-type table (it does not have the formatting options of the OTP script) and a special, limited-use/audience OTP script for split keys and variants at the end of this how-to.
This how-to also includes a procedure for building an SD card from scratch purely for the production of secure OTPs. Prior to that is some helpful info for those who are interested. If you wanted to build a good OTP generator, then this is for you…