It'll take me a while to wrap my head around this, and read through the (much clearer) paper you linked in your other reply, but I can't resist commenting on:

where block exchange looks like my triple reverse from last week:)

I laughed myself to sleep after reading: "There is a more elegant algorithm which is considered to be a part of folklore. blah blah blah. The proof of correctness is left to the reader."

No wonder, given their documentation methods. My proof:

abc12345
54321cba
12345cba
12345abc
[download]

Sor''d! :)