Mithril is a stake-based multi-signature scheme that leverages the existing Cardano network to provide certified snapshots of all or part of the blockchain state. These snapshots can be useful in multiple use cases such as secure voting, data exchange, and synchronization between applications, sidechains, light wallets, etc.
The first application of Mithril will allow faster bootstrapping of Cardano nodes. As each node has a full copy of the blockchain and needs to verify each block from the history, it takes a significant amount of time to start a new node from scratch. With Mithril, it is possible to start a node from a predefined state, with the same security guarantees that the chain itself provides, but much faster.