> ## Documentation Index
> Fetch the complete documentation index at: https://mintlify.com/Privacy-Cash/privacy-cash/llms.txt
> Use this file to discover all available pages before exploring further.

# MerkleTreeAccount

> The main account structure that stores the Merkle tree state for tracking private commitments

## Overview

The `MerkleTreeAccount` is a zero-copy account that stores the sparse Merkle tree state used to track all private commitments in the Privacy Cash protocol. Each tree can handle either native SOL or a specific SPL token.

## Account Structure

<ResponseField name="authority" type="Pubkey" required>
  The public key of the authority that can update this tree's configuration
</ResponseField>

<ResponseField name="next_index" type="u64" required>
  The index where the next leaf will be inserted in the Merkle tree
</ResponseField>

<ResponseField name="subtrees" type="[[u8; 32]; 26]" required>
  Array of intermediate node hashes representing the state of each level in the Merkle tree (height 26)
</ResponseField>

<ResponseField name="root" type="[u8; 32]" required>
  The current root hash of the Merkle tree
</ResponseField>

<ResponseField name="root_history" type="[[u8; 32]; 100]" required>
  Circular buffer storing the last 100 root hashes to allow proofs against recent tree states
</ResponseField>

<ResponseField name="root_index" type="u64" required>
  The current position in the root\_history circular buffer
</ResponseField>

<ResponseField name="max_deposit_amount" type="u64" required>
  Maximum amount (in lamports for SOL, or token units for SPL tokens) that can be deposited in a single transaction
</ResponseField>

<ResponseField name="height" type="u8" required>
  The height of the Merkle tree (fixed at 26)
</ResponseField>

<ResponseField name="root_history_size" type="u8" required>
  The size of the root history buffer (fixed at 100)
</ResponseField>

<ResponseField name="bump" type="u8" required>
  The PDA bump seed used for account derivation
</ResponseField>

<ResponseField name="_padding" type="[u8; 5]" required>
  Padding bytes required for zero-copy account alignment
</ResponseField>

## PDA Seeds

### For SOL (Native)

```
[b"merkle_tree"]
```

### For SPL Tokens

```
[b"merkle_tree", mint.key().as_ref()]
```

## Notes

* This account uses the `#[account(zero_copy)]` attribute for efficient memory access without deserialization
* The tree height of 26 allows for 2^26 (67,108,864) unique commitments
* The root history enables users to create proofs using recent tree states even while new deposits are being processed
* Each SPL token has its own separate Merkle tree account