- An ECDSA (secp256k1 curve) public/private keypair MUST be generated via a [BIP43](https://github.com/bitcoin/bips/blob/master/bip-0043.mediawiki) derived path from a [BIP39](https://github.com/bitcoin/bips/blob/master/bip-0039.mediawiki) mnemonic seed phrase.
- Status follows the X3DH prekey bundle scheme that Open Whisper Systems outlines [in their documentation](https://signal.org/docs/specifications/x3dh/#the-x3dh-protocol) with the following exceptions:
- Because there are no central servers, we do not publish one-time keys `OPK` or perform DH including them.
- A client MUST create X3DH prekey bundles, each defined by the following items:
- Identity Key: `IK`
- Signed prekey: `SPK`
- Prekey signature: `Sig(IK, Encode(SPK))`
- Timestamp
- These bundles are made available in a variety of ways, as defined in section 2.1.
- A client SHOULD regenerate a new X3DH prekey bundle every 24 hours. This MAY be done in a lazy way, such that a client that does not come online past this time period does not regenerate or broadcast bundles.
- The current bundle MUST be broadcast on a whisper topic specific to his Identity Key, `{IK}-contact-code`, intermittently. This MAY be done every 6 hours.
- A bundle MUST accompany every message sent.
- TODO: retreival of long-time offline users bundle via `{IK}-contact-code`
- A user MAY register a public username on the Ethereum Name System (ENS). This username is a user-chosen subdomain of the `stateofus.eth` ENS registration that maps to their whisper identity key (`IK`).
- An account MAY create a display name to replace the `IK` generated 3-word pseudonym in chat screens. This chosen display name will become part of the publicly broadcasted profile of the account.
- An account MAY edit the `IK` generated identicon with a chosen picture. This picture will become part of the publicly broadcasted profile of the account.
- Public group channels in Status are a broadcast/subscription system. All public messages are encrypted with a symmetric key drived from the channel name, `K_{pub,sym}`, which is publicly known.
- A public group channel's symmetric key MUST creation must follow the [web3 API](https://web3js.readthedocs.io/en/1.0/web3-shh.html#generatesymkeyfrompassword)'s `web3.ssh.generateSymKeyFromPassword` function
- In order to post to a public group channel, a client MUST have a valid account created (as per section [Account Creation Specification](./status-account-spec)).
- In order to listen to a public group channel, a client must subscribe to the channel name. The sender of a message is derived from the message's signature.
- Discovery of channel names is not currently part of the protocol, and is typically done out of band. If a channel name is used that has not been used, it will be created.
- A client MUST sign the message otherwise it will be discarded by the recipients.
Once you have the information of a contact, the following can be used to verify that the key material is as it should be.
#### Identicon
A low-poly identicon is deterministically generated from the whisper chat public key. This can then be compared out of band to ensure the reciever's public key is the one you have locally.
#### 3 word pseudonym / whisper key fingerprint
Status generates a deterministic 3-word random pseudonym from the whisper chat public key. This pseudonym acts as a human readable fingerprint to the whisper chat public key. This name also shows when viewing a contact's public profile and in the chat UI.
Status offers the ability to register a mapping of a human readable subdomain of `stateofus.eth` to their whisper chat public key. This registration is purchased (currently by staking 10 SNT) and stored on the Ethereum mainnet blockchain for public lookup.
