Rather than avoid deduplication (which is technically sound and benefits everyone), perhaps the solution to this is to make it impossible for DropBox itself to know who owns which files.
E.g. right now I assume a dropbox user owns a list of file ids with some metadata (e.g. that user's name for those files). If follows that if the government decides file XYZ is illegal then anyone with XYZ in their list is in trouble.
The user account could keep track of the total size of all the user's files and use arithmetic to keep it up-to-date, but not actually store the size of individual files except when they are "looked at".
So then the user's password (say) which is not itself stored is used to unlock stuff in the user's file table on a per request basis -- i.e. the actual file ids are only computed as needed. The actual mechanism doesn't need to be terribly secure, it just needs to be deniable. In other words without the user's password we simply cannot unambiguously determine which files are his or hers.
Comments
Rather than avoid deduplication (which is technically sound and benefits everyone), perhaps the solution to this is to make it impossible for DropBox itself to know who owns which files.
E.g. right now I assume a dropbox user owns a list of file ids with some metadata (e.g. that user's name for those files). If follows that if the government decides file XYZ is illegal then anyone with XYZ in their list is in trouble.
The user account could keep track of the total size of all the user's files and use arithmetic to keep it up-to-date, but not actually store the size of individual files except when they are "looked at".
So then the user's password (say) which is not itself stored is used to unlock stuff in the user's file table on a per request basis -- i.e. the actual file ids are only computed as needed. The actual mechanism doesn't need to be terribly secure, it just needs to be deniable. In other words without the user's password we simply cannot unambiguously determine which files are his or hers.