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Added tree hashing algorithm #120
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It's pretty dense. I would give some more motivation/explanation in the header.
Specifically, why this instead of a straight merkle tree? This allows for easy updates when isolated SSZ containers/lists are modified.
It would be nice to have an example of |
@mkalinin you can find this here: https://github.com/ethereum/beacon_chain/blob/vitalik_hash_ssz/hash_ssz.py I imagine @djrtwo will copy the code or something like it into the python impl once this gets finalized/approved. |
specs/simple-serialize.md
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chunkz.append(b'\x00' * CHUNKSIZE) | ||
chunkz = [hash(chunkz[i] + chunkz[i+1]) for i in range(0, len(chunkz), 2)] | ||
# Return hash of root and length data | ||
return hash(chunkz[0] + datalen) |
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nitpick: lst
/ chunkz
can be empty in the general case
Adds to the SSZ spec an algorithm for tree-hashing SSZ objects.
Experiments suggest that the hashing time required is increased by a factor of ~4-6, partly because Merkle hashing inherently raises the amount of data hashes due to multiple layers of hashing and partially because hash functions have a fixed computation cost in addition to the per-byte cost.