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Author Topic: Cryptocurrencies without transaction history  (Read 626 times)
babin
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May 09, 2013, 10:24:38 PM
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Hi all,

Since I'm newbie I need to create several posts on this forum, so here is mine)
I've noticed that all known (to me) cryptocurrencies are strore full transaction history for every available "coin". So, is to store this history really necessary? A simple alt. way may be just to store current balances of every user. Actually it even seems to enough to strore one-way accumulator hash of all balances and send required for every node hash update when new block is generated.
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Matthew N. Wright
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May 09, 2013, 10:25:46 PM
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Hi all,

Since I'm newbie I need to create several posts on this forum, so here is mine)
I've noticed that all known (to me) cryptocurrencies are strore full transaction history for every available "coin". So, is to store this history really necessary? A simple alt. way may be just to store current balances of every user. Actually it even seems to enough to strore one-way accumulator hash of all balances and send required for every node hash update when new block is generated.

If you can figure out how to do it without needing a blockchain, you'll have the only decentralized cryptocurrency in the world that doesn't require mining.

babin
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May 09, 2013, 10:29:01 PM
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I don't say that there no need of blockchain Smiley. Question is why there is need of transaction chain for every coin i.e. why balances information is not enough.
Matthew N. Wright
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May 09, 2013, 10:40:39 PM
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I don't say that there no need of blockchain Smiley. Question is why there is need of transaction chain for every coin i.e. why balances information is not enough.

Where does the balance information come from? Surely it would come from calculating all the transactions.

snail
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May 09, 2013, 10:41:47 PM
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You need the transaction history to make sure that someone hasn't spent the same bitcoins twice. If you store balance information, you still need the transaction history to verify that the balances are correct.
TheRobot
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May 09, 2013, 10:43:12 PM
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Transaction chain shows proof of which address owns which coins, and tracking them back to their initial mining proves they are real coins. Without this transaction chain it would be considerably easier to make illegitimate coins.
babin
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May 10, 2013, 12:10:54 AM
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I don't say that there no need of blockchain Smiley. Question is why there is need of transaction chain for every coin i.e. why balances information is not enough.

Where does the balance information come from? Surely it would come from calculating all the transactions.
Yes, but probably it is possible to decrease disk space/clients work-time if accumulate all transactions before the last checkpoint in one number per address - balance at the moment of last checkpoint.

You need the transaction history to make sure that someone hasn't spent the same bitcoins twice. If you store balance information, you still need the transaction history to verify that the balances are correct.
Transaction chain shows proof of which address owns which coins, and tracking them back to their initial mining proves they are real coins. Without this transaction chain it would be considerably easier to make illegitimate coins.
If we store balances before the checkpoint and transactions only after checkpoint it seems to be as safe as the current bitcoin implementation (beacuse balance at the time of the checkpoint won't change even in the case of some forks). The double spents could be easily verified - it only need to check that the sum of transaction inputs less then the balance.
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May 10, 2013, 12:20:27 AM
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So block 123,456 shows I (or more correctly an address I have) have a balance of 100 BTC.  How do you verify it?  If all you have is the balance how do you know it is correct?  If you can solve that problem then you can build a more efficient

Hint: miners might actually be attackers, scammers, thieves, etc.  In Bitcoin miners can't falsify coin records.  If they make a block which shows a "fake transaction" other nodes (which inherently DONT TRUST any other node) can verify the block is invalid a reject it.  How can they do that?  Because they can trace the history of every coin and thus can prove a tx is valid.

Don't start by thinking of how "X" would work.  Start by thinking of how someone could abuse/attack/defraud "X".  Remember this is money we are talking about here.
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May 10, 2013, 12:23:02 AM
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If we store balances before the checkpoint and transactions only after checkpoint it seems to be as safe as the current bitcoin implementation (beacuse balance at the time of the checkpoint won't change even in the case of some forks). The double spents could be easily verified - it only need to check that the sum of transaction inputs less then the balance.

Then you have to implicitly trust the entity making checkpoints.  Say you are a new user and you download the latest version of the client and it has a checkpoint for block 200,000 which says I have 100 BTC.  Prove that I do or don't legitimately have 100 BTC without any information prior to block 200,000.  What a developer owes me a lot of money so I say "you can pay your debt by putting a fake balance into the checkpoint for me".  There is no longer Satoshi's goal of commerce without a trusted third party. 

Remember the point of the blockchain is to decentralize verification and validation.  Any node, running any version of the client produced by anyone given a copy of the genesis block can prove every block and thus every current "balance" is valid.
babin
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May 10, 2013, 08:34:54 PM
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I still don't see where could be the problem)

Everything is similar to the current implementation of btc. Each block contain hash of previous and hash of concatenation of the all balances and proof of work of this block.
So block 123,456 shows I (or more correctly an address I have) have a balance of 100 BTC.  How do you verify it?  If all you have is the balance how do you know it is correct?
I can be sure that longest blockchain without its last 256 blocks is correct with prob > 1-2^(-256) (so it is easier to break some sha-256 from the network). When I get longest blockchain and transactions during last 256 blocks I can easily check if the transactions are correct and then check if the last 256 blocks are correct (that they are calculated from correct balances and check proof of work).

The problem that I see is that each adress actually still need to remember last balance before last 256 blocks of each address (remember only self balances and hashes of concat. balances of each block is not sufficient). But nevertheless it still seems to be much less to store then each transaction.
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May 10, 2013, 08:40:38 PM
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Hi all,

Since I'm newbie I need to create several posts on this forum, so here is mine)
I've noticed that all known (to me) cryptocurrencies are strore full transaction history for every available "coin". So, is to store this history really necessary? A simple alt. way may be just to store current balances of every user. Actually it even seems to enough to strore one-way accumulator hash of all balances and send required for every node hash update when new block is generated.

If you can figure out how to do it without needing a blockchain, you'll have the only decentralized cryptocurrency in the world that doesn't require mining.

A solution in my signature.
babin
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May 12, 2013, 11:50:53 AM
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Hi all,

Since I'm newbie I need to create several posts on this forum, so here is mine)
I've noticed that all known (to me) cryptocurrencies are strore full transaction history for every available "coin". So, is to store this history really necessary? A simple alt. way may be just to store current balances of every user. Actually it even seems to enough to strore one-way accumulator hash of all balances and send required for every node hash update when new block is generated.

If you can figure out how to do it without needing a blockchain, you'll have the only decentralized cryptocurrency in the world that doesn't require mining.

A solution in my signature.
You are talking about completely different cryptocurrency security model (and probably far not as secure as btc). But my question are there some bitcoin-like currencies (based on blockchains) that are not store transaction history. I described how it could be done and would like to see some critics or links to such altcoins.
Come-from-Beyond
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May 12, 2013, 11:52:28 AM
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You are talking about completely different cryptocurrency security model (and probably far not as secure as btc). But my question are there some bitcoin-like currencies (based on blockchains) that are not store transaction history. I described how it could be done and would like to see some critics or links to such altcoins.

There are no such currencies.
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May 12, 2013, 12:06:31 PM
 #14

This already exist look for ZEROCOIN
Come-from-Beyond
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May 12, 2013, 12:07:49 PM
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This already exist look for ZEROCOIN

Is it already implemented? I've seen only a whitepaper.
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