137 lines
5.2 KiB
Markdown
137 lines
5.2 KiB
Markdown
Dagger Contracts
|
|
================
|
|
|
|
An experimental implementation of the contracts that underly the Dagger storage
|
|
network. Its goal is to experiment with the rules around the bidding process,
|
|
the storage contracts, the storage proofs and the host stakes. Neither
|
|
completeness nor correctness are guaranteed at this moment in time.
|
|
|
|
Running
|
|
-------
|
|
|
|
To run the tests, execute the following commands:
|
|
|
|
npm install
|
|
npm test
|
|
|
|
To start a local Ethereum node with the contracts deployed, execute:
|
|
|
|
npm start
|
|
|
|
This will create a `deployment-localhost.json` file containing the addresses of
|
|
the deployed contracts.
|
|
|
|
Overview
|
|
--------
|
|
|
|
The Dagger storage network depends on hosts offering storage to clients of the
|
|
network. The smart contracts in this repository handle interactions between
|
|
client and host as they negotiate and fulfill a contract to store data for a
|
|
certain amount of time.
|
|
|
|
When all goes well, the client and host perform the following steps:
|
|
|
|
Client Host Storage Contract
|
|
| |
|
|
| --- request (1) --> |
|
|
| |
|
|
| <----- bid (2) ---- |
|
|
|
|
|
| ----------- create contract (3) ---------> |
|
|
| |
|
|
| ----- data (4) ---> | |
|
|
| |
|
|
| ---- start (5) ----> |
|
|
| |
|
|
| ---- proof (6) ----> |
|
|
| |
|
|
| ---- proof (6) ----> |
|
|
| |
|
|
| ---- proof (6) ----> |
|
|
| |
|
|
| <-- payment (7) ---- |
|
|
|
|
1. Client broadcasts off-chain a request for storage, containing the size of
|
|
the data that it wants to store and the length of time it wants to store it
|
|
2. Several hosts reply off-chain with a bid containing a price
|
|
3. The client selects a bid and uses it to create a new storage contract
|
|
on-chain
|
|
4. The client sends the data it wants to store to the host
|
|
5. Once the host has received the data it starts the storage contract
|
|
6. While the storage contract is active, the host proves that it is still
|
|
storing the data by responding to frequent random challlenges
|
|
7. At the end of the contract the host is paid
|
|
|
|
Contracts
|
|
---------
|
|
|
|
A storage contract can be created on-chain from a signed request and bid. The
|
|
request contains the size of the data and the length of time during which it
|
|
needs to be stored. It also contains proof requirements such as how often a
|
|
proof will need to be submitted by the host. A random nonce is included to
|
|
ensure uniqueness among similar requests. A bid contains a reference to the
|
|
request it pertains to, a price, and an expiry time.
|
|
|
|
When a new storage contract is created the client immediately pays the entire
|
|
price of the contract. The payment is only released to the host upon successful
|
|
completion of the contract.
|
|
|
|
Stakes
|
|
------
|
|
|
|
To motivate a host to remain honest, it must put up some collateral (stake)
|
|
before it is allowed to participate in storage contracts. The stake may not be
|
|
withdrawn as long as a host is participating in an active storage contract.
|
|
|
|
Should a host be misbehaving, then its stake may be reduced by a certain
|
|
percentage (slashed).
|
|
|
|
Proofs
|
|
------
|
|
|
|
A host is required to submit frequent proofs while a contract is active. These
|
|
proofs ensure with a high probability that the host is still holding on to the
|
|
data that it was entrusted with.
|
|
|
|
To ensure that a host is not able to predict and precalculate proofs, these
|
|
proofs are based on a random challenge. Currently we use the ethereum block hash
|
|
to determine two things: 1) whether or not a proof is required at this point in
|
|
time, and 2) the random challenge for the proof. Although a host will not be
|
|
able to predict the exact times at which a proof is required, the frequency of
|
|
proofs averages out to once per proof period. This proof period was agreed upon
|
|
by the client and host during the request/bid exchange.
|
|
|
|
Hosts have a small period of time in which they are expected to submit a proof.
|
|
When that time has expired without seeing a proof, validators are able to point
|
|
out the lack of proof. If a host misses too many proofs, it results into a
|
|
slashing of its stake.
|
|
|
|
To Do
|
|
-----
|
|
|
|
* Actual proofs
|
|
|
|
Because the actual proof of retrievability algorithm hasn't been determined yet
|
|
we're using a dummy algorithm for now.
|
|
|
|
* Contract take-over
|
|
|
|
Allow another host to take over a contract when the original host missed too
|
|
many proofs.
|
|
|
|
* Start failures
|
|
|
|
When a contract fails to start it should be aborted after a timeout. A
|
|
contract may fail to start because the client failed to send the data, or
|
|
because the host failed to start the contract. To discourage this, a small
|
|
portion of both the client and host money can be burned if the contract
|
|
doesn't start within a certain amount of time.
|
|
|
|
* Reward validators
|
|
|
|
A validator that points out missed proofs should be compensated for its
|
|
vigilance and for the gas costs of invoking the smart contract.
|
|
|
|
* Analysis and optimization of gas usage
|
|
|