87 lines
3.1 KiB
Markdown
87 lines
3.1 KiB
Markdown
# Payment Channels
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Payment channels are used to transfer funds between two actors.
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For example in lotus a payment channel is created when a client wants to fetch data from a provider.
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The client sends vouchers for the payment channel, and the provider sends data in response.
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The payment channel is created on-chain with an initial amount.
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Vouchers allow the client and the provider to exchange funds incrementally off-chain.
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The provider can submit vouchers to chain at any stage.
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Either party to the payment channel can settle the payment channel on chain.
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After a settlement period (currently 12 hours) either party to the payment channel can call collect on chain.
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Collect sends the value of submitted vouchers to the channel recipient (the provider), and refunds the remaining channel balance to the channel creator (the client).
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Vouchers have a lane, a nonce and a value, where vouchers with a higher nonce supersede vouchers with a lower nonce in the same lane.
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Each deal is created on a different lane.
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Note that payment channels and vouchers can be used for any situation in which two parties need to incrementally transfer value between each other off-chain.
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## Using the CLI
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For example a client creates a payment channel to a provider with value 10 FIL.
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```sh
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$ lotus paych get <client addr> <provider addr> 10
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<channel addr>
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```
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The client creates a voucher in lane 0 (implied) with nonce 1 (implied) and value 2.
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```sh
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$ lotus paych voucher create <channel addr> 2
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<voucher>
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```
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The client sends the voucher to the provider and the provider adds the voucher to their local store.
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```sh
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$ lotus paych voucher add <channel addr> <voucher>
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```
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The provider sends some data to the client.
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The client creates a voucher in lane 0 (implied) with nonce 2 (implied) and value 4.
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```sh
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$ lotus paych voucher create <channel addr> 4
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<voucher>
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```
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The client sends the voucher to the provider and the provider adds the voucher and sends back more data.
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etc.
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The client can add value to the channel after it has been created by calling `paych get` with the same client and provider addresses.
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```sh
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$ lotus paych get <client addr> <provider addr> 5
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<channel addr> # Same address as above. Channel now has 15
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```
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Once the client has received all their data, they may settle the channel.
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Note that settlement doesn't have to be done immediately.
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For example the client may keep the channel open as long as it wants to continue making deals with the provider.
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```sh
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$ lotus paych settle <channel addr>
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```
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The provider can submit vouchers to chain (note that lotus does this automatically when it sees a settle message appear on chain).
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The provider may have received many vouchers with incrementally higher values.
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The provider should submit the best vouchers. Note that there will be one best voucher for each lane.
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```sh
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$ lotus paych voucher best-spendable <channel addr>
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<voucher>
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<voucher>
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<voucher>
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$ lotus paych voucher submit <channel addr> <voucher>
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```
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Once the settlement period is over, either the client or provider can call collect to disburse funds.
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```sh
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$ lotus paych collect <channel addr>
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```
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