IMHO, that "middle" machine would be far more complex and expensive than the other two. A MITM attack might, theoretically, take only twice as long as attacking a single layer, the cost of doing so would be much more than twice as large. Anyone care to estimate what the cost of the RAM alone for the "MITM interface" machine would be? Let's see, for two 56 bit beys, you'd need storage for 2^57 blocks of 8 bytes each, or 2^60 bytes. At $40 per Mb, or so, that would come to ... let's see ... $4 * 10^51 for memory alone. And once the list of blocks started growing as the attack progressed, could the interface processor keep up with the other two, in real time? Massively parallel processors might speed both ends of the attack, but the "database comparison phase" would be the real bottleneck, IMHO. ... DAT tape, not RAM, I think. At $5 per GB I get $5*10^11 to hold the info. MITM requires a sort of this which requires roughly log(10^20) passes with a favorable constant. This will wear out a bunch of DAT drives but that is relatively minor. This is about an order of magnitude bigger than a project

At 00:18 1994/07/16 -0400, DAVESPARKS@delphi.com wrote: ... that I considered once to find the optimal solution to the Rubics cube.