Storage & Databases

Merkle tree

Tree of hashes; root commits to all leaves.


In plain terms

Ralph Merkle, 1979. Bitcoin, Git, ZFS, Certificate Transparency, IPFS. Inclusion proofs are O(log n) hashes.

Origin

Ralph Merkle, "A Certified Digital Signature," 1979. The same Merkle who later invented public-key cryptography. Bitcoin (2009) made Merkle trees a household name in tech.

Where it shows up in production
  • Bitcoin block headers Each block commits to all its transactions via the Merkle root.
  • Git Tree objects are Merkle trees over directory contents. Commit hashes commit transitively to everything.
  • Certificate Transparency logs Append-only Merkle trees; inclusion proofs are O(log n) hashes.
On Semicolony
Sources & further reading
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