# Provider
A provider is an entity (individual, business, etc.) that operates an Airnode to serve one or more APIs to smart contracts. Each provider has only one private key, which they use across all chains.
# providerId
Providers are identified by their providerId, which is of type bytes32.
A provider's providerId is derived from their private key, and there is a one-to-one mapping between the two.
Since the provider uses the same private key across all chains, they will have the same providerId across all chains.
To derive providerId in Solidity:
providerId = keccak256(abi.encode(masterWalletAddress));
To derive providerId in JS (using ethers.js):
providerId = ethers.utils.keccak256(ethers.utils.defaultAbiCoder.encode(['address'], [masterWalletAddress]));
where masterWalletAddress is the address of the wallet derived from the private key of the provider with the path m.
(For deriving wallets from a private key using a path, see HD wallets (opens new window).)
Here is an example of how one derives the master wallet address from the mnemonic in JS (using ethers.js):
masterHdNode = ethers.utils.HDNode.fromMnemonic(mnemonic);
masterWalletAddress = masterHdNode.address;
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# Creating a provider record
Before being able to serve on a chain, a provider has to have a record created.
To do this, the provider's master wallet has to be used to call createProvider() of ProviderStore.sol, where the contract assigns the corresponding providerId as such:
function createProvider(
address admin,
string calldata xpub
)
external
payable
override
returns (bytes32 providerId)
{
providerId = keccak256(abi.encode(msg.sender));
...
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Note that since msg.sender is used to derive the providerId, no one but the provider can claim their providerId on any chain.
This provider record creation is done automatically by Airnode.
The provider only needs to fund their master wallet for it to be able to afford this transaction, and the master wallet will send the remaining funds to providerAdmin along with this transaction.
The Airnode deployment displays instructions for how to do this, and the masterWalletAddress is included in the receipt that the deployer outputs for future reference.
# providerAdmin
providerAdmin is an address that is authorized to update provider-related properties (e.g., endpoint authorizers).
Airnode sets a providerAdmin while creating the provider record, and this is sourced from config.json under the name providerAdminForRecordCreation.
providerAdmin can transfer its authority to another address.
The master wallet can reclaim the authority by calling createProvider() and setting another providerAdmin.
# xpub
The provider announces their extended public key (xpub) in ProviderStore.sol for requesters to be able to derive their designated wallets.
The xpub that the provider has announced is not verified on-chain.
However, the requester can verify it off-chain.
For example, in JS (using ethers.js):
hdNode = ethers.utils.HDNode.fromExtendedKey(xpub);
masterNode = hdNode.derivePath('m');
providerIdDerivedFromXpub = keccak256(abi.encode(masterNode.address));
assert(providerIdDerivedFromXpub === providerId);
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See the section about designated wallets to see how requesters can use xpub to derive their designated wallets.
# Setting endpoint authorizers
An important responsibility of the providerAdmin is to set endpoint authorizers.
Authorizers are used to enforce rules about which requests will be responded to, and this can be used to enforce KYC, monthly subscription payments, etc.
See the sections about endpoints and authorizers for more details.