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Merge pull request #182 from ethereum/vbuterin-patch-1 

tree_hash -> SSZTreeHash
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Hsiao-Wei Wang 2018-11-28 12:38:10 +08:00 committed by GitHub
parent 3253936517 05be2f05e3
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specs/simple-serialize.md
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@ -390,7 +390,7 @@ return typ(**values), item_index
### Tree Hash
The below `tree_hash` algorithm is defined recursively in the case of lists and containers, and it outputs a value equal to or less than 32 bytes in size. For the final output only (ie. not intermediate outputs), if the output is less than 32 bytes, right-zero-pad it to 32 bytes. The goal is collision resistance *within* each type, not between types.
The below `SSZTreeHash` algorithm is defined recursively in the case of lists and containers, and it outputs a value equal to or less than 32 bytes in size. For the final output only (ie. not intermediate outputs), if the output is less than 32 bytes, right-zero-pad it to 32 bytes. The goal is collision resistance *within* each type, not between types.
We define `hash(x)` as `BLAKE2b-512(x)[0:32]`.
@ -435,13 +435,13 @@ def merkle_hash(lst):
return hash(chunkz[0] + datalen)
```
To `tree_hash` a list, we simply do:
To `SSZTreeHash` a list, we simply do:
```python
return merkle_hash([tree_hash(item) for item in value])
return merkle_hash([SSZTreeHash(item) for item in value])
```
Where the inner `tree_hash` is a recursive application of the tree-hashing function (returning less than 32 bytes for short single values).
Where the inner `SSZTreeHash` is a recursive application of the tree-hashing function (returning less than 32 bytes for short single values).
#### Container
@ -449,7 +449,7 @@ Where the inner `tree_hash` is a recursive application of the tree-hashing funct
Recursively tree hash the values in the container in order sorted by key, and return the hash of the concatenation of the results.
```python
return hash(b''.join([tree_hash(getattr(x, field)) for field in sorted(value.fields)))
return hash(b''.join([SSZTreeHash(getattr(x, field)) for field in sorted(value.fields)))
```