Summary: CDs of images are vulnerable; encryption is possible and new DICOM mechanisms could make it easier; does the threat really justify the inconvenience and cost?
Recently there has been increasing interest in providing some sort of secure DICOM CD so that at least not just anybody can read the contents of such a CD that is lost or stolen. An Aunt Minnie post exemplifies the concern.
DICOM does provide mechanisms to encrypt the CD (using the same tools as are used for S/MIME secure email), but they are rarely, if ever, used in practice.
I am not sure whether this is because a) most people don't care about security or b) reading CDs is hard enough without adding an extra barrier or c) the mechanisms in DICOM are too complicated to deploy.
It is easy enough to extend DICOM to support security mechanisms that are "easier" to deploy and don't require a priori knowledge of every recipient and the use of certificates and a public key infrastructure, such as a password-based encryption mechanism, and I have put in a CP to do so (adding RFC 3211 PKCS#5-based PBE for the KEK to CMS, for those who care), but ...
... my real question is, would anybody want to use it ?
Deployment would require sending a "password" "separately" from the CD (e.g., in an email), and probably keeping track of these in order to answer calls from recipients who have lost or forgotten it, days, weeks or years later. There is no question that this would also make importing of old studies from old CDs as priors more likely to fail.
I don't think the industry will be able to resist demands to provide such capabilities from those with serious (if not excessive) privacy zeal, but is the cure worse than the disease in terms of the cost and complication it will trigger ?
If we are going to have to do this, obviously using a standard DICOM mechanism is preferable to any proprietary scheme, to support 3rd party viewers and PACS importation; however, such devices would have to be upgraded to support the DICOM media security profile. In the interim an on-media viewer that supported the DICOM encryption scheme would at least make the images viewable, though there are many reasons why on-board viewers are undesirable that don't need to be reiterated here.
With modern processors, the speed of encryption/decryption should not be a rate limiting step compared to reading the physical media, although with media that is faster than CD or DVD, such as USB memory sticks, there might be some compromises with respect to number of iterations and key length to consider.