With a view on using a tool similar to fgcombinefs in cloud situations, I would need a writable n-of-m Shamir secret sharing filesystem.
As a matter of routine security, I do not want the cloud provider to be able to reconstruct real data from what I store on his hardware.
If the data stored on his hardware is fundamentally random, because it is just one share in a Shamir shared secret, there is no point for anybody to try to look for a key, because there isn't one. The attacker would simply need find the other
n-1 shares, stored at other cloud providers elsewhere on the globe.
fgcombinefs seems to implement 99% of the job, but unfortunately, its Shamir filesystem is read-only.
When looking at the fuse operations behind
fgcombinefs, you can see that both
write are actually supported :
int(* write_buf )(const char *, struct fuse_bufvec *buf, off_t off, struct fuse_file_info *) int(* read_buf )(const char *, struct fuse_bufvec **bufp, size_t size, off_t off, struct fuse_file_info *)
You can see that in the case of writing a block, fuse will ask you to effectively perform a write to the file named as in the first string argument
const char *, at offset
off_t off. In the case of a read of a block in a file at a particular offset and a particular size, fuse will ask you to allocate a block, if needed, and return its address in
I would think that writing a Shamir block, amounts to first producing the
m Shamir secret shares, and then writing them to the
m underlying filesystems, while reading a Shamir block amounts to picking
n filesystems from the
m available, ask them to send the block, recombine the
n secrets on the fly, and return the reconstituted block to the caller.
In these circumstances, I do not really understand why writing to a Shamir filesystem would fundamentally be unsupported?
However, if I overlooked an impossibility somewhere, I would be most grateful if someone pointed it out, because it would spare me the time wasted in trying to program something that would in fact be impossible. Is there fundamentally a reason why the author has made