Devcon3 - Debrief #3 - Whisper = Ethereum's (confidential) Email System
In my view, private communications between individuals should remain private. This is one of the objectives of the whisper project.
Whisper is the Ethereum Virtual Machines' communication protocol that allows decentralised applications (dApps) and individuals to communicate with each other in a confidential manner.
Examples of potential use cases include dApps that need to publish small amounts of information to each other and have the publication last some substantial amount of time, dApps that need to signal to each other in order to ultimately collaborate on a transaction and dApps that need to provide hinting or general communications between each other to carry out their functions.
For example, a currency exchange dApp may use it to record an offer to sell some currency at a particular rate on an exchange. In this case, it may last anything between tens of minutes and days. The offer wouldn't be binding, merely a hint to get a potential deal started.
Currently, Whisper allows for secure transient publication and subscription of messages using a novel topic-based routing system. In general, Whisper allows ‘transactions of information’ between dApps. The data that is transacted does not require consensus, will not be archived, is not binding and does not require a state change to the blockchain.
The Devcon3 presentation is here.