Per-File Encryption Support in NT4?

tesserae asks: "I'm a consultant in the aerospace industry, and some of my clients have indicated that they'd like to see me encrypt any data I have on their projects. Because I have to maintain file format compatibility with them, I run NT4 (since the use of M$ Office is nearly universal in this industry). I do have a box running Windows 2000 Pro, which supports transparent per-file encryption, but I don't want to switch to W2k on all my machines. How might I go about hacking a per-file encryption capability into NTFS under NT4? A friend suggested a 'loopback filesystem with a ramdisk with PGP over the whole thing,' but was unable to tell me how to do it. (His friends did it under Linux which is not an option with me, unfortunately)."

"Is there another dependable approach? (Something like installing Service Pack 6, then converting the data disk to NTFS5... but somehow I doubt that NT4 has the capability of managing per-file encryption, even if it reads/writes NTFS5 with the proper SP.)

The reason I'm interested in transparent per-file encryption is that I use many documents (and apps) simultaneously, and don't need to be slowed down with encrypting/decrypting individual files or directories -- and it would help if the .tmp files M$ apps create were also encrypted, for additional security."