You missed something critical posted by the AC. He said you have to assign a unique prime number to each user. Not simply a number.
The 30 millionith prime is 573259391. The 50 millionith prime is 982451653. I couldn't find the 60 millionith prime anywhere, and another 20M should be enough room for the corporations. In either case ceil(log2(573259391)) == ceil(log2(982451653)) == 30. The beauty of this is you can multiply two large primes, take the modulo and somebody with the primes can still verify/extract them later: This isn't very different from doing RSA crypto with very short primes...

Look for a used LTO3/LTO4 tape drive, then bulk-buy tapes.
Write each set of content to two tapes, ideally of different brands, and store in different places if you're really concerned.

I've been backing up to LTO3 tapes for ~3 years now, i've got 50+ tapes, mostly in my safety deposit box at the bank (cost $75/year)

LTO4 based on eBay prices right now would be an initial expenditure of ~$1k for the drive, and $25-30 per 800GB of storage.

The cloud options aren't really feasible for me, as the upload time & bandwidth cost is horrendous.

http://dev.gentoo.org/~tove/stats/gentoo-x86/cvs-log-sum.txt

I'm number 20 on that list, having recently surpassed 10k commits to Gentoo myself (in 7 years). The top of our list is somebody with 70k commits.

- robbat2@gentoo

I use the Watt's Up Pro, but it's for monitoring a single outlet.

Do you intend to monitor your entire house, or just some devices?

I have the original WiSpy model, from when they first hit the market, and I still use it extensively.

It's been insanely useful in tracing the problems, just put it on a laptop, with a long USB extension cable, and wander around. I will admit that I've only used it on Linux, as I don't have any Windows around, but it's been perfectly suited to my needs.

A friend of mine was having a similar interference problem, during a subset of hours, and I traced it to one of the neighbours that would prepared dinner while using a set of wireless headphones.