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  1. ---
  2. order: 9
  3. ---
  4. # Light Client Protocol
  5. Light clients are an important part of the complete blockchain system for most
  6. applications. Tendermint provides unique speed and security properties for
  7. light client applications.
  8. See our [light
  9. package](https://pkg.go.dev/github.com/tendermint/tendermint/light?tab=doc).
  10. ## Overview
  11. The objective of the light client protocol is to get a commit for a recent
  12. block hash where the commit includes a majority of signatures from the last
  13. known validator set. From there, all the application state is verifiable with
  14. [merkle
  15. proofs](https://github.com/tendermint/spec/blob/953523c3cb99fdb8c8f7a2d21e3a99094279e9de/spec/blockchain/encoding.md#iavl-tree).
  16. ## Properties
  17. - You get the full collateralized security benefits of Tendermint; No
  18. need to wait for confirmations.
  19. - You get the full speed benefits of Tendermint; transactions
  20. commit instantly.
  21. - You can get the most recent version of the application state
  22. non-interactively (without committing anything to the blockchain). For
  23. example, this means that you can get the most recent value of a name from the
  24. name-registry without worrying about fork censorship attacks, without posting
  25. a commit and waiting for confirmations. It's fast, secure, and free!
  26. ## Where to obtain trusted height & hash?
  27. https://pkg.go.dev/github.com/tendermint/tendermint/light?tab=doc#TrustOptions
  28. One way to obtain semi-trusted hash & height is to query multiple full nodes
  29. and compare their hashes:
  30. ```sh
  31. $ curl -s https://233.123.0.140:26657:26657/commit | jq "{height: .result.signed_header.header.height, hash: .result.signed_header.commit.block_id.hash}"
  32. {
  33. "height": "273",
  34. "hash": "188F4F36CBCD2C91B57509BBF231C777E79B52EE3E0D90D06B1A25EB16E6E23D"
  35. }
  36. ```
  37. ## HTTP proxy
  38. Tendermint comes with a built-in `tendermint light` command, which can be used
  39. to run a light client proxy server, verifying Tendermint rpc. All calls that
  40. can be tracked back to a block header by a proof will be verified before
  41. passing them back to the caller. Other than that, it will present the same
  42. interface as a full Tendermint node.
  43. ```sh
  44. $ tendermint light supernova -p tcp://233.123.0.140:26657 \
  45. -w tcp://179.63.29.15:26657,tcp://144.165.223.135:26657 \
  46. --height=10 --hash=37E9A6DD3FA25E83B22C18835401E8E56088D0D7ABC6FD99FCDC920DD76C1C57
  47. ```
  48. For additional options, run `tendermint light --help`.