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- ---
- order: 13
- ---
-
- # Light Client
-
- Light clients are an important part of the complete blockchain system for most
- applications. Tendermint provides unique speed and security properties for
- light client applications.
-
- See our [light
- package](https://pkg.go.dev/github.com/tendermint/tendermint/light?tab=doc).
-
- ## Overview
-
- The light client protocol verifies headers by retrieving a chain of headers,
- commits and validator sets from a trusted height to the target height, verifying
- the signatures of each of these intermediary signed headers till it reaches the
- target height. From there, all the application state is verifiable with
- [merkle proofs](https://github.com/tendermint/spec/blob/953523c3cb99fdb8c8f7a2d21e3a99094279e9de/spec/blockchain/encoding.md#iavl-tree).
-
- ## Properties
-
- - You get the full collateralized security benefits of Tendermint; no
- need to wait for confirmations.
- - You get the full speed benefits of Tendermint; transactions
- commit instantly.
- - You can get the most recent version of the application state
- non-interactively (without committing anything to the blockchain). For
- example, this means that you can get the most recent value of a name from the
- name-registry without worrying about fork censorship attacks, without posting
- a commit and waiting for confirmations. It's fast, secure, and free!
-
- ## Security
-
- A light client is initialized from a point of trust using [Trust Options](https://pkg.go.dev/github.com/tendermint/tendermint/light?tab=doc#TrustOptions),
- a provider and a set of witnesses. This sets the trust period: the period that
- full nodes should be accountable for faulty behavior and a trust level: the
- fraction of validators in a validator set with which we trust that at least one
- is correct. As Tendermint consensus can withstand 1/3 byzantine faults, this is
- the default trust level, however, for greater security you can increase it (max:
- 1).
-
- Similar to a full node, light clients can also be subject to byzantine attacks.
- A light client also runs a detector process which cross verifies headers from a
- primary with witnesses. Therefore light clients should be set with enough witnesses.
-
- If the light client observes a faulty provider it will report it to another provider
- and return an error.
-
- In summary, the light client is not safe when a) more than the trust level of
- validators are malicious and b) all witnesses are malicious.
-
- Information on how to run a light client is located in the [nodes section](../nodes/light-client.md).
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