How to eliminate liability?
This is just an idea I thought I would throw out and see what happens. There has been considerable discussion recently about datahavens, how no one physical location in meatspace is safe, and how there is no single place on earth that a datahaven could exist that would accept all kinds of information. Well, what about spreading the information out? Something simple like doing a matrix rotation on the scrambled data in 8 byte blocks and splice it by bit to split the data up, add ECC (error correction code) to it, and spread it to several servers. This way no one server has all the information necessary to recreate the "offending" information and if one server gets "hit" (killed), the information can still be regenerated from the the information and ECC from the other servers. The bit splitting I'm talking about would go something like this. The data would be set up in clusters of eight bytes and then these eight bytes would be rotated, error correction applied, divided byte by byte to separate queues (for separate destinations), resequenced to include the ECC overhead, and sent on it's merry way. Original encrypted information: Cluster A Cluster B... Byte 1: 01001011 Byte 2: 10101110 Byte 3: 10010110 Byte 4: 10110111 Byte 5: 01011100 Byte 6: 10111011 Byte 7: 10001101 Byte 8: 00110110 After the matrix rotate: Cluster A Cluster B... Byte 1: 01110110 Byte 2: 10001000 Byte 3: 01010101 Byte 4: 00111101 Byte 5: 11001110 Byte 6: 01111011 Byte 7: 11110101 Byte 8: 10010110 Add ECC: Cluster A Cluster B... Byte 1: 01110110 1 Byte 2: 10001000 0 Byte 3: 01010101 0 Byte 4: 00111101 1 Byte 5: 11001110 1 Byte 6: 01111011 0 Byte 7: 11110101 0 Byte 8: 10010110 0 ECC byte: 01000000 0 Divided up: Cluster A ECC-A Cluster B ECC-B Byte 1: 01110110 1 10100011 0 Resequenced into separate queues by byte in cluster: 01110110 11010001 10...... ...and distributed to the servers. These are just my ramblings, I'm not a programmer (or at least I haven't been for a long time). Nor do I claim to know if this form of distribution will escape the legal issues of storing certain data on on servers in specific areas of meatspace (I'm no lawyer (kill the lawyers)). At the very least, it seems that this scheme (or something like it, if this form of ECC is not sufficient) could be used to keep data from being lost if one or more servers gets whacked by armed forces or a nuclear bomb. I'm not even going to think about how this data could be distributed. You guys can do that... Feedback and flames welcome. John estoy@hotmail.com ______________________________________________________ Get Your Private, Free Email at http://www.hotmail.com
At 09:23 PM 1/22/98 PST, John M wrote:
There has been considerable discussion recently about datahavens, how no one physical location in meatspace is safe, and how there is no single place on earth that a datahaven could exist that would accept all kinds of information. Well, what about spreading the information out? Something simple like [...] and spread it to several servers. This way no one server has all the information necessary to recreate the "offending" information and if one server gets "hit" (killed), the information can still be regenerated from the the information and ECC from the other servers.
Secret Sharing is easy, and there are a number of implementations with useful properties like being able to read the original from K of N parts.* The problem is how to implement it in ways that protect the server operators as well as the information providers. For instance, the author's client software can do the split and send the shares too different servers, and make sure the readers know how to find the pieces; this can even be automated enough to make it convenient. This not only makes it hard for the Bad Guys to find the pieces, it makes it impossible for the data haven provider to know what's being stored there, and even if the site is siezed it doesn't give up the critical information. This is a Good Thing, and we've discussed it. On the other hand, what happens if a Bad Guy wants to entrap the operator, by planting child pornography, pirated software, and TOP SECRET data in the data haven, advertising on Usenet and then calling the cops. Anybody, including the cops, can retrieve the contraband and bust them. So what are the alternatives, besides obviously encrypting your disks so it's harder to determine what's on them besides the plant, and the ever popular "don't let them find your physical location"? Perhaps the data haven can do the split and farm the data out to other data havens - but how do they know the data they're receiving is really a slice of contraband data instead of Yet Another Plant? It gets pretty convoluted. [* You can read about secret sharing in Schneier. ] Thanks! Bill Bill Stewart, bill.stewart@pobox.com PGP Fingerprint D454 E202 CBC8 40BF 3C85 B884 0ABE 4639
John M wrote:
Well, what about spreading the information out? Something simple like doing a matrix rotation on the scrambled data in 8 byte blocks and splice it by bit to split the data up, add ECC (error correction code) to it, and spread it to several servers. This way no one server has all the information necessary to recreate the "offending" information and if one server gets "hit" (killed), the information can still be regenerated from the the information and ECC from the other servers.
This seems like another variation of the 'reverse secret-sharing' schemes, independently proposed by Jim McCoy, Matt Ghio, and others. Cooper and Birman give a good theoretical introduction at http://cs-tr.cs.cornell.edu/TR/CORNELLCS:TR95-1490 although their scheme uses only the simple XOR instead of a full matrix. Ghio's version is at http://infinity.nus.sg/cypherpunks/dir.archive-97.06.12-97.06.18/0391.html Neither paper goes heavily into linear algebra, but the scheme can easily be extended to martices in a finite field, xor being the special case of mod 2. The idea's been around for awhile; it'd be nice to see a working implementation (hint, hint).
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