Mark writes:

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I still don't see why all of the actual encryption couldn't be done in software though...

Me either, apart from TEMPEST issues...

Speed. No software implementation will be able to match a hardware DES chip in total throughput. I have enough trouble dealing with the drive transfer speeds imposed upon PC unix systems with the lame bus, but even this could keep up if I had to run my file access through a software DES system. There are cards out there that can do this, and it doesn't really make sense not to offload this to an external device.

Linux comes with slot in file system modules (as detailed in a letter to Jim) that you can easily adapt to your own uses. Ive been playing around with this idea for a while. Adding a desfs(tm) (me :) to a linux kernel is not going to be that hard I think.. (touch wood).

Yes, the other thing that pushed me to linux (besides the larger user community) was the support for "drop-in" filesystems. jim

Ryan Alan Porter writes:

Jim McCoy wrote: [regarding why to use hardware for the encryption]

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Speed. No software implementation will be able to match a hardware DES chip in total throughput. [...] There are cards out there that can do this, and it doesn't really make sense not to offload this to an external device.

Yes, actually it does. Hardware cannot be widely and freely distributed the way software can. I am looking to write something that can protect EVERYONE, not just those people that can afford to buy some dedicated hardware.

This is true, but I am not completely writing-off those without the ability to get a hardware card: they will just have to put up with the, IMHO, unbearable slowness of doing filesystem encryption through software. I am also examining the log-structured filesystem (Rosenblum and Osterhout) to see if using that as the core to add the encryption to will make the system useable without hardware. Additionally, perhaps the fact that there is some real use for a hardware DES card will get people to buy them and increase their availability in general...

Would PGP be so widespread today if it required a hardware coprocessor?

No. Then again PGP is for encrypting _files_, not filesystems. We are talking several orders of magnitude difference in the amount of data you are trying to force through them. I guess part of the difference in viewpoints we have is that I am spoiled on unix. I have become used to the high-bandwidth drives and networks that I use every day and would not be able to stand the bottleneck created by doing the encryption in software.

I like the whole Unix idea for PC's in general, and Linux in particular, but the fact remains that the people who need security the most (the average schmuck out there in the business world or the kid running a BBS) are most likely to be using a PC DOS-based system, and I am writing for them.

Yes, a crypto drop-in that works like Stacker would be a good thing to have available and I wish you the best of luck in your efforts. On the general DOS side though, I can run DOS under linux and have a DOS filesystem within a linux system as well (linux plug :) Either way, good luck. jim