The ability to do this has been in and around the Government for awhile now. Data At Rest (DAR) is the official program and policies that are used, though there are different COTS options for it. The reason it hasn't been widely adopted is that it complicates an already complicated situation. The people who go TDY with official government computers tend to be higher ranking officers and senior managers. They are not technically proficient and always seem to break something or need help to access the VPN or other piece of software. Something like DAR adds another item that these individuals could inadvertently break, and as their TDY you can't just send a tech over to their desk to fix the problem. The worst part is the IT manager tends to answer to these officials or to the people who work for these officials, so every-time a problem happens, whether it's user error or not (btw you CAN NOT say user error when the user is a high ranking official) it looks bad on your department. The result is the IT managers want as few potential problems as possible, so DAR has been put off and avoided whenever possible.