# <center><i class="fa fa-edit"></i> 1.2 Hash Pointer and Data Structures </center>
###### tags: `Blockchain`
The following notes are taken from [Coursera](https://www.coursera.org/learn/cryptocurrency/home/week/2)

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### Hash Pointer
- Pointer to where some info is stores
- Cryptographic hash of info
- Ask to get info back
- Verify info has not changed

### Linked List with Hash Pointers (Blockchain)
- tamper-evident because of the head or `H()`

### Binary Tree with Hash Pointers (Merkle Tree)
- Show O(log n) items to verify the tree
- log n is usually time/space
- Variant: Sorted Merkle Tree
- Can verify non-membership
- Show consecutive bocks where member is supposed to be in between the two
:::success
Generally: can use hash pointers in any pointer based data structure that has **no cycles**
:::