Re: [bitcoin-dev] [bitcoin-discuss] Checkpoints in the Blockchain.

[Damian Williamson <willtech@live.com.au>]

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I do understand your point, however, 'something like stuxnet' cannot be used to create valid data without re-doing all the PoW. Provided some valid copies of the blockchain continue to exist, the network can re-synchronise.


Unrelated, it would seem useful to have some kind of deep blockchain corruption recovery mechanism if it does not exist; where blocks are altered at a depth exceeding the re-scan on init, efficient recovery is possible on detection. Presumably, it would be possible for some stuxnet like thing to modify blocks by modifying the table data making blocks invalid but without causing a table corruption. I would also suppose that if the node is delving deep into the blockchain for transaction data, that is would also validate the block at least that it has a valid hash (apart from Merkle tree validation for the individual transaction?) and that the hash of its immediate ancestor is also valid.


Regards,

Damian Williamson


________________________________
From: bitcoin-discuss-bounces@lists.linuxfoundation.org <bitcoin-discuss-bounces@lists.linuxfoundation.org> on behalf of Dave Scotese via bitcoin-discuss <bitcoin-discuss@lists.linuxfoundation.org>
Sent: Sunday, 20 May 2018 11:58 AM
To: Scott Roberts
Cc: Bitcoin Discuss
Subject: Re: [bitcoin-discuss] Checkpoints in the Blockchain.

I wouldn't limit my rendering to words, but that is a decent starting point.  The richer the rendering, the harder it will be to forget, but it needn't all be developed at once. My goal here is to inspire the creation of art that is, at the same time, highly useful and based on randomness.

Anyway, I asked what "premise that this is needed" you meant and I still don't know the answer.

"The archive is a shared memory" - yes, a shared computer memory, and growing larger (ie more cumbersome) every day. If something like stuxnet is used to change a lot of the copies of it at some point, it seems likely that people will notice a change, but which history is correct won't be so obvious because for the humans whose memories are not so easily overwritten, computer data is remarkably non-memorable in it's normal form (0-9,a-f, whatever).  If we ever want to abandon the historical transaction data, having a shared memory of the state of a recent UTXO Set will help to obviate the need for it.  Yes, of course the blockchain is the perfect solution, as long as there is exactly one and everyone can see that it's the same one that everyone else sees.  Any other number of archives presents a great difficulty.

In that scenario, there's no other way to prove that the starting point is valid.  Bitcoin has included a hardcoded-checkpoint in the code which served the same purpose, but this ignores the possibility that two versions of the code could be created, one with a fake checkpoint that is useful to a powerful attacker.  If the checkpoint were rendered into something memorable at the first opportunity, there would be little question about which one is correct when the difference is discovered.

On Sat, May 19, 2018 at 5:22 PM, Scott Roberts <wordsgalore@gmail.com<mailto:wordsgalore@gmail.com>> wrote:
I just don't see the point of needing to know it any different from the hex value. Or maybe I should say I can't imagine it being useful because I can't imagine what you're after is possible. There might be a theoretical proof that what you're after is impossible. Hard to forget is almost the opposite of many options and what we're trying to do is decide between many options. I'll assume English because  it's the only starting point I have that's even in the ballpark of being possible. You might need to constrain the word selection and the structure in which you put it. I can only imagine that you are talking about putting the words into some sort of story. The only kind of story that would be hard to forget  is one that  fits into an overall structure that we are familiar with but those types of structures are few  compared to the possibilities that we're trying to encode. "Hard to deny" is a type of "hard to forget". Besides trying to connect it to external reality or history that we can all agree on there is also an internal consistency that could be used like a checksum such as the structure I mentioned. The only thing that seems to fit the bill is the blockchain itself. It's on everyone's computer so it's impossible to forget and it has internal consistency. Is the only shared memory we have that can't be subject to a Sybil attack or other hijacking of our memory of the true history. Our translation of the hash into words and a story could potentially be subject to hijacking if it's not done perfectly correct. It just seems best to me to use the hash itself. They archived existence of the prior parts of the blockchain are what make that particular hash hard to forget. Supposedly it can't be forged to reference  a fake history. The archive is a shared memory that fits the encoding rules.

On Sat, May 19, 2018, 4:30 PM Dave Scotese <dscotese@litmocracy.com<mailto:dscotese@litmocracy.com>> wrote:
Did you mean the premise that we have "the need to retain the full blockchain in order to validate the UTXO Set"?

I hadn't thought of just making it easier to remember, as your suggestion does (12-13 words), and that's a great idea.  I have passphrases of that kind, but I noticed a kind of mandela effect<https://www.snopes.com/news/2016/07/24/the-mandela-effect/> just with myself.  For example, I one of the words I chose was like "olfactory" but after a few months, what I remembered was like "ontology". The solution I came up with is to couple the data with far more items than we normally do.  Every ten minutes, we get a new set of 256 bits that can be used to create something potential very difficult to forget, and that's what I'm after.

An algorithm could be used to do this with the Bip39 word list.  If we categorized the words according to parts of speech, the bits could be used to determine which word goes next in a kind of ad-lib, but this creates a phrase that is only memorable in the language for which the algorithm is developed.  As a thought experiment, I'll try adjective noun verb(as past tense) noun preposition adjective adjective noun: Stuff would come out like "Able abstract abused accident across actual adult affair."  not memorable at all, but sense can be made of it and sometimes the sense will be remarkable.  As it is, I will have forgotten it in an hour or two.

On Thu, May 17, 2018 at 4:29 PM, Scott Roberts <wordsgalore@gmail.com<mailto:wordsgalore@gmail.com>> wrote:
I disagree with your premise that this is needed, I like the question. Humans are experts at language and I don't think we have another repository at hand that we can categorize for memory that is better than words. Using words is a common way of doing what you're thinking about. If the checkpoint could be a hash that meets a difficulty target the possibilities are 2^182 at the current hashrate instead of 2^256. So we need only 12 or 13 common words with their various possible endings (30,000).  I would find it easier to insert  a letter and 3 numbers after every 2 words so there would be only 8 words used. There are probably other tricks people have figured out but there can't be any kind of advanced encoding because it wouldn't benefit more than one word. There might be a way to convert the words into something that almost sounds like English sentences but it would probably come out a cost of at least doubling the number of words.

On Thu, May 17, 2018, 12:13 PM Dave Scotese via bitcoin-discuss <bitcoin-discuss@lists.linuxfoundation.org<mailto:bitcoin-discuss@lists.linuxfoundation.org>> wrote:
I got the idea that a SHA256 hash could be rendered into something difficult to forget.  The rendering would involve using each of the 256 bits to specify something important about the rendering - important in an instinctive human-memory way.

Let's assume such a rendering is possible, and that at any time, any person can execute the rendering against the SHA256 hash of a consistent representation of the UTXO Set.  Sometimes, someone will execute the rendering and discover that it is remarkable in some way (making it even more memorable), and therefore will publish it.

The published, memorable rendering now becomes a kind of protection against any possible re-writing of the blockchain from any point prior to that UTXO Set.  When everyone involved in Bitcoin recognizes this protection, it relieves us of the need to retain the full blockchain in order to validate the UTXO Set at that point, because enough people will recognize it, and it can be validated without reference to any kind of prior computer record.

This does leave open the possibility that an attacker could create a more favorable UTXO Set that happens to have a rendering similar enough to fool people, or one that has exactly the same SHA256-hash, but that possibility is remote enough to ignore (just as we all ignore the possibility that whatever creates the master seed for our HD wallet will create a unique master seed).

I've been working on how such a rendering could happen.  It could describe music, characters, colors, plot points, memorable elements of characters, etc.

Dave Scotese

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I like to provide some work at no charge to prove my value. Do you need a techie?
I own Litmocracy<http://www.litmocracy.com> and Meme Racing<http://www.memeracing.net> (in alpha).
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"He ought to find it more profitable to play by the rules" - Satoshi Nakamoto



--
I like to provide some work at no charge to prove my value. Do you need a techie?
I own Litmocracy<http://www.litmocracy.com> and Meme Racing<http://www.memeracing.net> (in alpha).
I'm the webmaster for The Voluntaryist<http://www.voluntaryist.com> which now accepts Bitcoin.
I also code for The Dollar Vigilante<http://dollarvigilante.com/>.
"He ought to find it more profitable to play by the rules" - Satoshi Nakamoto

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