Synchronous two-party payment channel

Specially for people who will test (TON Team)

We already setted up private keys, and deplyed contract for you, however, you can use your own keys and deploy contract again - but it will take more steps.

We will not attach pk and other hardcoded data to our github: https://github.com/button-tech/ton-sync-payments-channel

DEMO: We also have a video demo how to run all of that stuff: https://www.youtube.com/watch?v=GUhWrnylGDk

Thank you for a contest, it was great challenge for us, BW Team

Running

What do you need for running it:

You need to create a catalog with wallet.addr and wallet.pk files (account with Grams).

1. Deploy Smart contract on TON

Go to contract/pool folder

We assume that you will use alice.pk and bob.pk with addresses, but you can create your own.

For ./bind_commands.sh script You can see the details in contract folder

1. Get seqno of giver

runmethod 0:e4b867748f26658f1fb18e9e0e755edbe2c7650a2bafadbd216f94c3142385e2 seqno

2. Run ./deploy.sh
   3)Enter non-bouncable address
   4)Seqno of giver 5)Done

Else you need to:
1)Run fift pool.fif
2)Get money on future contract address
3)Send .boc to the network

Important: You need docker.io to run CLI, we assume that it is installed on machine

For the server you need to run with a port like:

1. First terminal window:

docker run -it -p port:port -v path_to_catalog_with_files:/app/data prazd/synchannel:new

2. Second terminal window:

docker run -it -v path_to_another_catalog_with_files:/app/data prazd/synchannel:new

3. Enter smart contract address:

 0:E6DE901D76CDC66C2269201280658DA017D04A75619D8BE5E63E104FA5F6F477

4. Setup peer to peer connection

A person who deployed Smart Contract has to serve connection with command

Terminal 1:

    serve

Then you need to choose a port where your connection will be served:

Please, enter a source port or enter "exit": 3000
To make connection use this address in LAN:
/ip4/172.17.0.3/tcp/3000/p2p/QmeZ1Ykwj57BGqeSjU66pvh5iDfSYjW2EugqaFkZ5UENYw

To make connection use this address in WAN (if you have public IP):
/ip4/178.140.100.51/tcp/3000/p2p/QmeZ1Ykwj57BGqeSjU66pvh5iDfSYjW2EugqaFkZ5UENYw

Waiting for incoming connection

Later you need to copy this link and sent it to your partner (person 2)

LAN for local

or

WAN for public

/ip4/172.17.0.3/tcp/3000/p2p/QmeZ1Ykwj57BGqeSjU66pvh5iDfSYjW2EugqaFkZ5UENYw

The partner has to run

    connect

And enter connection string there

/ip4/172.17.0.3/tcp/3000/p2p/QmeZ1Ykwj57BGqeSjU66pvh5iDfSYjW2EugqaFkZ5UENYw

If connection is successful, the address and signature will be automatically exchanged with your partner. That will prove that it is yours addresses

You will get something like this:

Partner signature: 78FB74C5FDD013648BF060663AF55DE25566D310021D5F448403168890F85C80D6339A1EC63C6917823B9CAA3F6EB95819334C0F7AB70FD34F54A733FCF2010A
Partner address: kQDI-VEsKDl-v8HFpyl51HrNmwWX-37ZXLNu9PvsHglupowG

5. We have a smart contract, let's deposit money to it from each terminal:

Terminal 1:

    deposit

You will see your wallet balance in GRAMS

Your account balance now: 38.433277 Gram

Enter amount to put on contract or "exit"

Next, you need to enter GRAMs amount that you will send to the contract

Your partner has to repeat the same operation

After notification

❗ Received initial state❗

One of the last of 2 people who made the deposit needs to sign the initial state with command

 sign

And after that, you can run command showAll and see something like this

Sender A
A [3.000000 4.000000] B
Step 1
Signs A [F 3] B

All commands:

serve			  create connection token
connect			  connect to other peer
deposit			  make deposit
send			  send some amount
sign			  sign last state
balanceContract          show balance of contract in workchain
balanceChan	          show balance in sync chan
balanceTon               show balance in workchain
getAccount               show user ton account
getPartnerAccount        show partner ton account
getSmartContractAccount  show smart contract address
getSeqno                 show seqno of your acc in workchain
createEmpty 		  create empty state
requestEmpty		  request empty state from your partner
showAll			  show all states
showLast		  show last state
withdraw                 push actual state in to workchain
exit			  exit from app

6. Right now you can send an offchain transaction from Terminal 1 (The first state num can be sent only from it)

Terminal 2:

send 1 or send .1 or send 0.1

You will get information at Terminal 1:

❗ Received new state❗

and then you need to approve and sign the new state that Terminal 2 sent to you:

showLast
sign
showAll

Sender A
A [3.000000 4.000000] B
Step 1
Signs A [F 3] B

Sender B
A [3.200000 3.800000] B
Step 2
Signs A [7 9] B

So, at Terminal 1 you will see a confirmation, now it is Terminal 2 turn to send transaction

❗ Last state signed successful❗

If you want to make transaction to your partner but now is not your turn you can use command requestEmpty

Then your partner will see a notification:

❗ Your partner request empty state❗

If you agree with that you can create an empty state by command createEmpty

and your partner should sign it

7. Let's do a withdraw:

Terminal 1:

withdrawal  

Then you need to enter step number that you want to send to the contract:

Enter step number: 2
Signature A: 73A6FADA9F3FA985BB000404AD1FAC434FE12AE310EC2390522AA9B42843C3301FA52026BF7BFEA460E2FC7413D6CD67DDB76BB455DCD634A1C9437843B9AA0A
Signature B: 97A45EDC329F58B6B50C9D78CFEE2AC2D9C6A160D806E6D8C0F5CC5E36537FE73156DF834102CD84953A3AE133D3E47897652D7F0AFB24F50A4FE5136801E003
Balance A: 3.200000
Balance B: 3.800000
Account signature: 78FB74C5FDD013648BF060663AF55DE25566D310021D5F448403168890F85C80D6339A1EC63C6917823B9CAA3F6EB95819334C0F7AB70FD34F54A733FCF2010A
Partner signature: 6C6A86A1A5D1CCA53FD60620B0871AA0F8CCEA00655F0B1AEEF4D2F5F981C4AE6937988D42C423DFF43F81C6D0F49ABB9966F0984D4FE4362338479457B78609
Step: 2
Contract seqno: 3
Are you sure[y/n]:y

Next, if transaction completed, your partner will see a notification:

❗ Your partner sent the state to the smart contract❗

And partner further can do a withdrawal too

After that two person will see all information about result balances:

Success withdrawal!
Your balance in workchain now: 37.014310
Partner balance in workchain now: 52.548630
Smart contract balance in workchain now: 0.932511

With CLI you can withdraw peacefully, however, it could be another option:

If there is a conflict in smart contract, you can withdraw it by applying the latest state

You can see all the states by:

showAll 

Details of implementation

TON WP was used as a theoretical base.

We have:

User 1 (A), User 2 (B)

Smart contract (SC)

1 Before deposit (Onchain + Offchain):

We assume that A and B will have a secure p2p connection between each other. We use our own implementation on Golang.

A and B have to exchange the public keys, ton wallet addresses and signatures that prove the accuracy of the address.

Also, someone needs to deploy and pay for gas on SC, so we assume that A and B already have reached an agreement about that.

2 Deposit (Onchain):

A and B send a query from TON Wallet to SC. They need to send GRAMS and initial details of the state.

Initial details of state:

Variables	Description
Public Key A	Needs to check signatures and owners of contract
Public Key B	Needs to check signatures and owners of contract
Amount A	Needs to check that total sum A + B during exit will be correct
Amount B	Needs to check that total sum A + B during exit will be correct

Amount A and B are calculated based on the amount that A and B will send to SC

3 Sending GRAMs to each other (Offchain):

It is Sync Channel, so only one of A and B can send GRAMs to each other.

But we implemented a possibility to request your turn. If you request it, B will have to just sign to the old state with a new state_num +=1

We use our client to send GRAMs as well

4 Withdraw (Onchain)

Case with the same states:

Each of A and B has to send:

Variables	Description
Amount A	Amount of GRAMs that will be sent to A
Amount B	Amount of GRAMs that will be sent to B
State_num	Current amount of all transactions between A and B offchain
pool_address	Address of current SC to make signature unique per contract
slice_ref with signature A	Check that A agreed with current state
slice_ref with signature B	Check that A agreed with current state

Case with conflict:

If A applied to withdraw and then B applied with conflict.

A has an option to send another state that has state_num > than current

If it is provided, withdraw will be executed with this state

Authors

Nick Kozlov - CTO and Co-founder of BUTTON Wallet (@enormousrage, nk@buttonwallet.com)

Kirill Kuznecov - Co-founder of BUTTON Wallet (@krboktv, kk@buttonwallet.com)

Alexey Prazdnikov - Fullstack developer at BUTTON Wallet (@noprazd, ap@buttonwallet.com)

Max Spiridonov - Lead Backend developer at BUTTON Wallet (@maxSpt, ms@buttonwallet.com)

Ivan Frolov - Backend developer at BUTTON Wallet (@ivnkhh, if@buttonwallet.com)

Artem Vorobev - Lead Developer at BUTTON Wallet ( @artall64 artem@buttonwallet.com )

Roman Semenov - One of the founders of Copperbits community, co-author of Tornado.cash Ethereum mixer (@poma, semenov.roma@gmail.com)

Igor Gulamov Blockchain Researcher and Entrepreneur (@igor_gulamov, igor.gulamov@gmail.com)