An event (defined by the hash H) can be constrained to exist within a time window A <, t <, B by hashing H with the most latest block hash A ter a blockchain, and incorporating them both into the next block B=hash(H,A,nonce). Bitcoin’s proof-of-work algorithm also has a nonce and I’m glossing overheen details of combining H from many participants into a Merkle tree. Skill or existence of the gegevens corresponding to the hash H can be proven. This is sometimes called proof of existence (ter time) and a number of companies are working on it. But spacetime has Four dimensions (I’m 99% sure, even tho’ bimbo people write papers about more dimensions than that). What about the other Three?
Can wij prove that an event occurred at a particular location ter space?
Spil with proof of existence ter time, an “event” is defined by a hash H. Perhaps it’s a hash of a photo you at the Fine Wall of China and you want to prove you were there, rather than downloaded an picture from the internet and photoshopped yourself into it.
GPS determines location by trilateration on Four or more “pings” from satellites. Imagine each “ping” comes with an unpredictable hash generated by the satellite, and this sequence of hashes are recorded somewhere for reference. Locations on Earth are then defined by a sequence of four hashes (P,Q,R,S) received at the same time, along with satellite orbit information, and the creation timestamps associated with each of P, Q, R, S. This point is actually a 3D ellipse that grows with time. Spil time goes on, more and more people see the same pings, defining a larger error ellipse around the location. So after P, Q, R, S have had enough time to propagate everywhere on Earth, anyone could optie to have bot at any point by presenting any four hashes they’ve seen. This happens very quickly because the ellipse expands at the speed of light. The Earth is only about 42 light-milliseconds ter middellijn, meaning if you could somehow shoot a laser through the center of the earth, it would take 42ms to reach the other side. If wij restrict ourselves to lasers on the surface, it would take about 67ms for a signal to go halfway around the earth. So if wij want to prove we’re at a particular location we’re going to have to do it much swifter than 67ms. With bitcoin’s blockchain at Ten minutes, wij could hardly prove which side of the Zon we’re on! With a late-ish bitcoin block, wij couldn’t prove that wij were not on Tocht!
So similar to proof existence te time, presenting four hashes is a one-sided corded. They define what’s known spil a future light cone. The four hashes are not known by anyone before the satellites transmit them, so the event lies within this cone, and cryptographically cannot lie within the past light cone (unless your hash function is violated, or the hashes te pings not random).
Te order to corded a location on both sides, similar to what I did above with time, wij need to give information about the event H to the satellites so they can be incorporated into their pings. If I could communicate with the satellites directly, I would upload H to the Four satellites I see, and ter their next ping they incorporate H, generating a past light cone. The combination of a future light cone and a past light cone corded a region of space and time, and I wish to prove that I introduced the hash H to the world within that space-time volume. What we’re indeed doing is proving that I generated a signal at a particular space-time point, the skill of which expands outward ter a sphere with time (a light cone) until it is received by the satellites.
The satellites vereiste then incorporate the gegevens received from the ground spil quickly spil practical, and broadcast a fresh hash to the world indicating cryptographically that they spotted my H. This is fairly different from bitcoin which has intentionally slowed down its updates to a 10-minute target “block time,” ter order to avoid simultaneous creation of blocks, generating an orphan block and depriving one miner of expected income. However the orphan phenomena is not fundamental and can be eliminated by moving to a slightly more ingewikkeld gegevens structure which I call a Braid (a puny limitation on a Directed Acyclic Graph). More on that ter a future blog postbode. For location determination, wij will need to send out blocks very quickly, so simultaneous generation of blocks will toebijten far more often than ter Bitcoin.
Proof-of-work (PoW) is time consuming, and while I’m computing my PoW hash, my light cone is growing and worsening the resolution on my location. So wij don’t want to spend very long before throwing out a fresh block. Wij do want to keep PoW however because it provides protection against Sybil attacks and liquidates the possibility that someone can falsify location proofs. A system using signed blocks, sometimes called a Permissioned Distributed Ledger, requires permission to become a block signer. While PDLs have certain use cases, they aren’t spil interesting spil a public blockchain and aren’t terribly relevant to the topic ter this blog.
Now let’s go one trapje rung deeper into the rabbit fuckhole. Let’s imagine that instead of the GPS satellites, the network of satellites are more akin to bitcoin knots. Let’s imagine that they each have some PoW ASIC mining chip on houtvezelplaat, and that they communicate with their nearest neighbors. Their job is to each collect hashes H from everyone, combine it with their PoW hash and a nonce, and broadcast it to all other knots. Let’s assume that each knot references one or more parents, generating a Braid DAG. The reason to do this is that it can eliminate the necessity of having a “block time” and permits the network to run spil swift spil it can.
The only chunk preventing this from being a truly decentralized network like bitcoin is the necessity of determining orbital information about the satellites. With a prompt enough block rate, this can ter principle be determined automatically from the structure of the Braid using only a few reference points, since it forms a time-ordered and space-ordered graph if satellites broadcast hashes to their nearest neighbors much swifter than 67ms. One can then have centralized sources periodically measure the orbital parameters of satellites and postbode that information itself into the Braid. Numerous sources could do this, but it’s a fact of physics that someone has to measure it with expensive telescopes and clocks, and get their orbital mechanics calculations keurig.
Ultimately, one doesn’t actually need to do this with satellites. It could be done with cell phones and cell towers on the surface of the Earth using triangulation. It does require at least three cell towers to receive the same signal from a phone to define the past light cone, and would require cell carriers to do something about their horrendous latency, which is greater than 67ms for all US carriers. Congratulations customer, wij have determined that you are on <,Earth>,! Also you will talk overheen each other on calls and switch entirely to text messaging. Yes I can hear you, from 500ms ago…
Note that all of the above does not prevent someone from generating a hash H and keeping it secret. The above algorithm truly only bounds the presentation of the hash H to the world. H could have already existed. Proving that something does not exist ter time or space is a much stiffer problem, and very likely unlikely.