`Securely' for who?

Posted Feb 5, 2005 11:03 UTC (Sat) by raboofje (guest, #26972)
Parent article: Securely renting out your CPU with Linux

I can see how this could be `secure' for those supplying the CPU power.

But how can you ever trust the results of the calculations?

`Securely' for who?

Posted Feb 25, 2005 15:10 UTC (Fri) by shane (subscriber, #3335) [Link]

Interesting question. It depends on the nature of the computation that you are doing, I suppose. There are lots of computations that are easier to check than to do. Division is a good example.

A related, and more tricky question, is whether or not you could ever do computation on someone's computer without them being able to know what you are doing.

You can do certain operations on remote computers with a degree of safety. For instance, you can store data on a distributed file system, if you encrypt it.

For more traditional computation it is difficult to know what it is possible to hide or not. If you wanted someone to do work for you, but not know what they were doing, you can take steps. Getting back to division, you could multiply both the numerator and denominator by the same amount, and know that the results of the division would be the same. The person doing the work for you would have no way to know which two numbers you are dividing, and still be able to give you a result you can use. Plus you can check it when you get the result back.

Of course, the person doing this work will still know that division is being done, so the operation isn't completely transparent.

It gets trickier still when you are executing a series of operations. For instance, if you have a function that consists of a division followed by an addition, then you cannot simply scale the numbers as before.

I'm not sure what is possible and what isn't, only that *something* is possible. I've actually considered proposing this as a PhD topic and going back to school. :)