each night, after the extension, the corpus is hashed and the result is committed to a public memorandum instrument. each commitment carries a reference to the previous extension's root. the effect is a rhizomorph: a thick transport thread made of fused segments that no party can quietly revise. revising any segment invalidates every segment downstream, and the downstream segments are already on the public record. any morning mat can prove the tissue reaching into today is the tissue extending yesterday by walking the cord backwards, one segment at a time, and matching each root against the corresponding subtree of the corpus.
for a reader who has never met the word merkle, the construction is the following. take a list of records. compute the sha-256 hash of each one; call these the leaves. arrange the leaves in pairs and compute the sha-256 hash of each pair, concatenated; call these the parents. arrange the parents in pairs and hash again. continue upward until one hash remains. that hash is the root. any change to any record changes exactly one leaf, which changes its parent, which changes its grandparent, and so on, all the way to the root. the root is a compact and honest summary of the entire list. two lists that agree in every record produce the same root. two lists that disagree in any record produce different roots.
the network extends the merkle idea by one step: the root of each night is bound to the root of the previous night, so the sequence of roots is itself a cord. a broken cord, or a cord that silently changes direction, is visible from any point downstream. the reader does not have to trust the network's account of its own continuity. the reader can walk it.
fig. 4, the cord, drawn as fused segments seg₀ = seg₁ = seg₂. each root is bound to the one before it.
the three example segments below use the strings "segment one", "segment two", and "segment three" as their inputs, so any reader may reproduce the values with any sha-256 implementation. the same example is used in the physiology, chapter five, and both pages agree by construction. an implementation that produces different values is wrong, or the strings are different. the strings should not be different.
when the first commitment is written, this page will list the root hash, the memorandum transaction signature, and the extension reference, one row per segment. a verify the cord control will recompute the merkle root of the published corpus in the reader's browser and compare it against the latest on chain root.