This EIP introduces the new `contenthash` field for ENS resolvers, allowing for a better defined system of mapping names to network and content addresses. Additionally the `content` and `multihash` fields are deprecated.
Multiple applications including [Metamask](https://metamask.io/) and mobile clients such as [Status](https://status.im) have begun resolving ENS names to content hosted on distributed systems such as [IPFS](https://ipfs.io/) and [Swarm](https://swarm-guide.readthedocs.io). Due to the various ways content can be stored and addressed, a standard is required so these applications know how to resolve names and that domain owners know how their content will be resolved.
The field `contenthash` is introduced, which permits a wide range of protocols to be supported by ENS names. Resolvers supporting this field MUST return `true` when the `supportsInterface` function is called with argument `0xbc1c58d1`.
The value returned by `contenthash` MUST be represented as a machine-readable [multicodec](https://github.com/multiformats/multicodec). The format is specified as follows:
The encoding of the value depends on the content type specified by the protoCode. Values with protocodes of 0xe3 and 0xe4 represent IPFS and Swarm content; these values are encoded as v1 [CIDs](https://github.com/multiformats/cid) without a base prefix, meaning their value is formatted as follows:
When resolving a `contenthash`, applications MUST use the protocol code to determine what type of address is encoded, and resolve the address appropriately for that protocol, if supported.
In order to support names that have an IPFS or Swarm hash in their `content` field, a grace period MUST be implemented offering those name holders time to update their names. If a resolver does not support the `multihash` interface, it MUST be checked whether they support the `content` interface. If they do, the value of that field SHOULD be treated in a context dependent fashion and resolved. This condition MUST be enforced until at least March 31st, 2019.
To support `contenthash`, a new resolver has been developed and can be found [here](https://github.com/ensdomains/resolvers/blob/master/contracts/PublicResolver.sol), which has been deployed at [0xd3ddccdd3b25a8a7423b5bee360a42146eb4baf3](https://etherscan.io/address/0xd3ddccdd3b25a8a7423b5bee360a42146eb4baf3)
