Comment by schiffern

This hardly proves the NSA has nothing up their sleeve.

If I was the NSA, I'd just make a huge rainbow table of all (timestamp hashes, passphrase hashes of every book/movie, random sentences, etc), then generate huge numbers of (seed, secret key) pairs and pick the first one that matches.

Voila. All the crypto backdoor and a side of plausible deniability if anyone decodes the seed.

Bonus points if the exact "rainbow table" algorithm couldn't recover the original seed, so that's why NSA couldn't tell us where it came from. :)