[WIP] Payment channel example. #2431

chriseth · 2017-06-21T15:03:02Z

No description provided.

axic · 2017-06-21T21:54:37Z

docs/solidity-by-example.rst

+        uint closeBalanceUser0;
+        enum State { Opened, Accepted, Closing, Closed }
+        State state;
+        function Channel(address _other, uint _timeout) payable {


I think some whitespaces between functions, state variables and the pragma cannot hurt.

axic · 2017-06-21T21:56:10Z

docs/solidity-by-example.rst

+            timeout = _timeout;
+        }
+        function accept() payable {
+            require(msg.sender == users[1]);


Since user[0] and user[1] have a very specific role, I think it would make sense naming them appropriately.

Initiator and acceptor?

That sounds fine.

chriseth · 2017-06-22T09:54:06Z

This is work in progress and requires much more documentation. You could already check whether the contract is a valid payment channel, though.

axic · 2017-07-11T11:47:20Z

docs/solidity-by-example.rst

+            state = State.Accepted;
+        }
+        function requestClose(uint _balanceUser0, uint _sequenceNumber, uint8 v, bytes32 r, bytes32 s) {
+            require(state == State.Accepted || state == State.Closing);


Why allow closing multiple times? Each time the timestamp/balance/sequence is updated.

@chriseth this is still an open question

axic · 2017-07-12T09:37:08Z

I suggest not to merge this before #2553.

axic · 2017-07-13T21:14:11Z

Rebased to trigger the tests.

axic · 2017-07-19T01:47:39Z

docs/solidity-by-example.rst

+            require(state == State.Opened);
+            state = State.Accepted;
+        }
+        function requestClose(uint _balanceUser0, uint _sequenceNumber, uint8 v, bytes32 r, bytes32 s) {


Inconsistency: v/r/s is not prefixed.

axic · 2017-12-12T02:41:36Z

@chriseth updating this with the comments. Can you review? What is left to merge this?

axic · 2018-02-26T23:20:38Z

@chriseth rebased. What is blocking this?

axic · 2018-02-26T23:23:15Z

docs/solidity-by-example.rst

+            require(_sequenceNumber > closeSequenceNumber);
+            require(_balanceInitiator <= 2 * deposit);
+            require(closeTimestamp == 0 || now <= closeTimestamp + timeout);
+            require(ecrecover(sha3(_balanceInitiator, _sequenceNumber), _v, _r, _s) == counterpartyAddress(_sequenceNumber));


Should use keccak256.

axic · 2018-02-26T23:40:38Z

Compilation failures:

Warning: This is a pre-release compiler version, please do not use it in production.
/tmp/tmp.aEq6oBGgwl/test_0a4d82f0af2c945e6a612af13a590776a772d071cdf8cbc0cce41dba326a8ffb.sol:14:9: Warning: No visibility specified. Defaulting to "public".
        function PaymentChannel(address _other, uint _timeout) payable {
        ^
Spanning multiple lines.
/tmp/tmp.aEq6oBGgwl/test_0a4d82f0af2c945e6a612af13a590776a772d071cdf8cbc0cce41dba326a8ffb.sol:23:9: Warning: No visibility specified. Defaulting to "public".
        function accept() payable {
        ^
Spanning multiple lines.
/tmp/tmp.aEq6oBGgwl/test_0a4d82f0af2c945e6a612af13a590776a772d071cdf8cbc0cce41dba326a8ffb.sol:34:9: Warning: No visibility specified. Defaulting to "public".
        function requestClose(uint _balanceInitiator, uint _sequenceNumber, uint8 _v, bytes32 _r, bytes32 _s) {
        ^
Spanning multiple lines.
/tmp/tmp.aEq6oBGgwl/test_0a4d82f0af2c945e6a612af13a590776a772d071cdf8cbc0cce41dba326a8ffb.sol:46:9: Warning: No visibility specified. Defaulting to "public".
        function close()
        ^
Spanning multiple lines.
/tmp/tmp.aEq6oBGgwl/test_0a4d82f0af2c945e6a612af13a590776a772d071cdf8cbc0cce41dba326a8ffb.sol:15:13: Error: Undeclared identifier. Did you mean "initiator"?
            initator = msg.sender;
            ^------^
/tmp/tmp.aEq6oBGgwl/test_0a4d82f0af2c945e6a612af13a590776a772d071cdf8cbc0cce41dba326a8ffb.sol:49:70: Error: Undeclared identifier. Did you mean "counterpartyAddress"?
            require(now >= closeTimestamp + timeout || msg.sender == counteryPartyAddress(closeSequenceNumber + 1));
                                                                     ^------------------^
/tmp/tmp.aEq6oBGgwl/test_0a4d82f0af2c945e6a612af13a590776a772d071cdf8cbc0cce41dba326a8ffb.sol:52:17: Error: Undeclared identifier. Did you mean "initiator"?
            if (initator.send(closeBalanceInitiator))
                ^------^

redsquirrel · 2018-02-27T04:27:18Z

docs/solidity-by-example.rst

+            initator = msg.sender;
+            acceptor = _other;
+            deposit = msg.value;
+            require(deposit < 2**250);


I'm curious about this overflow check on msg.value. I wouldn't think to do that... is it really necessary?

Not sure why I did this. Perhaps better safe than sorry?

chriseth · 2018-02-27T10:00:20Z

Some more comments are left to merge this. I actually would have liked to also include the frontend part. We can add a comment that this is still left to do.

axic · 2018-03-27T14:41:44Z

@bit-shift @ekpyron do you want to write some actual Solidity code ^^? 😉

smarx · 2018-05-14T16:14:35Z

@chriseth asked me to adapt my code from https://programtheblockchain.com/posts/2018/05/11/state-channels-for-two-player-games/ to go in the documentation.

I wonder, though, if the code from https://programtheblockchain.com/posts/2018/02/23/writing-a-simple-payment-channel/ (or perhaps https://programtheblockchain.com/posts/2018/03/02/building-long-lived-payment-channels/) might be better? That's a one-way payment channel, which is simpler to get right (and thus simpler code).

I guess I'm asking what the goal is here. If it's to get across the fundamentals of state channels, then maybe my state channel post is the most appropriate starting point. If it's to introduce payment channels, then I think my "simple payment channel" post is a good starting point.

If the goal is just to show how signatures can be used to make off-chain commitments, then https://programtheblockchain.com/posts/2018/02/17/signing-and-verifying-messages-in-ethereum/ is perhaps an even better starting point.

I'm happy to adapt any of those to a short example for the documentation, but I'd love some guidance on what people want to see.

chriseth · 2018-05-14T17:43:19Z

I think the goal is to show how easy it is to implement payment channels in etherem as opposed to bitcoin ;)

If a two-sided payment channel is too complicated, then a one-sided will do. It would be great if it could also include the required javascript code (or at least a snippet).

From a didactic point of view, it is probably a good idea to first have a short chapter on how to to create and verify signatures and then another chapter about how that can be used in payment channels.

chriseth · 2018-05-14T17:46:24Z

Added an issue, perhaps someone is willing to put up a bounty for this: #4131

chriseth · 2018-05-28T10:46:30Z

@smarx did you have time to work on this yet?

smarx · 2018-06-06T22:38:58Z

@chriseth No, sorry, I didn't. Looked like someone else is starting on the bounty, though!

chriseth · 2018-07-05T16:08:26Z

There are much better examples now.

axic · 2018-07-24T22:36:59Z

This was obsoleted by #4212.

chriseth added the in progress label Jun 21, 2017

axic reviewed Jun 21, 2017

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chriseth changed the title ~~Payment channel example.~~ [WIP] Payment channel example. Jun 22, 2017

axic reviewed Jul 11, 2017

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axic force-pushed the paymentchannel branch from 0ba09ee to 736d4a8 Compare July 13, 2017 21:13

axic reviewed Jul 19, 2017

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axic added the documentation 📖 label Aug 28, 2017

axic mentioned this pull request Oct 10, 2017

Add Micropayment channel #3063

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axic force-pushed the paymentchannel branch from 736d4a8 to 0298044 Compare December 12, 2017 02:40

chriseth and others added 2 commits February 27, 2018 00:20

Payment channel example.

20052c1

Payment channel example: replace user0/user1 with initiator/acceptor

5891d87

axic force-pushed the paymentchannel branch from 0298044 to 5891d87 Compare February 26, 2018 23:20

axic reviewed Feb 26, 2018

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redsquirrel reviewed Feb 27, 2018

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chriseth mentioned this pull request May 28, 2018

Payment channel tutorial #4131

Closed

chriseth closed this Jul 5, 2018

axic deleted the paymentchannel branch July 24, 2018 22:37

[WIP] Payment channel example. #2431

[WIP] Payment channel example. #2431

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chriseth commented Jun 21, 2017

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chriseth commented Jun 22, 2017

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axic commented Jul 12, 2017

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chriseth commented Feb 27, 2018

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smarx commented May 14, 2018 •

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