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Author: Admin | 2025-04-28
Where the backup left off. All the backup service needs to do is start at the end of the list you provide from your phone and work its way back until it gets a matching result. So whenever there isn’t a match, the backup service simply goes backward one result at a time through the list of hash outputs to see if it gets a match with the cloud backup. As soon as it finds a match, it knows that’s the point it is in sync with and only needs to copy everything from that point on. The backup service doesn’t need to confirm the accuracy of anything that came earlier! For example, If the cloud backup’s final hash result matches with the 997th output in our phone’s list of hashes, the backup would know the following: It is a perfect match for all the first 997 photos in the photo library on the phone. It would know this without having to look at any one of those photos or any of the previous 996 hash results! And then it would know to copy only the final three photos, just 18 megabytes, instead of all 6 gigabytes.Bitcoin Chains Blocks, Not PhotosIn the above example, we used photos because we’re all familiar with them. We showed how we could use hashes to chain together hashes of photos with actual photos in order, one at a time. This allowed us to create and maintain a perfect backup without having to go through the whole database each time a new photo was added. The efficiency was incredible and ensured 100% complete accuracy in each photo in the library and even in the order of the library itself.We may be less familiar with what Bitcoin blocks are than what photos are. However, hashes don’t care what the input is, so what works with the photo library example also works for what Bitcoin does with blocks of transactions.Bitcoin doesn’t maintain just one single perfect backup of its database of blocks, though — it maintains as many backups as there are people who run Bitcoin nodes. Tens of thousands of people all over the world are able to copy and keep perfect, up-to-date copies of its database that is hundreds of gigabytes in size with minimal computational effort and minimal data transmission. How? By relying on chaining together these tiny hash results. As long as the hash of the last block they have matches that of the network, they can know with perfect certainty that all the data in all the blocks, from the genesis block until the latest block, is 100% precisely identical to that of everyone else’s.This is because every Bitcoin node acts similarly to the backup service in the example above. It starts with the hash of the genesis block (which was represented by photo #1 in the above example) and hashes it together with the data from the incoming block. And this keeps going on, one block at a time, every time
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