Set the merkle tree depth to 32.

proofs/spend.pism

@@ -4,7 +4,7 @@ constant G_SPEND FixedGenerator
 constant PRF_NF BlakePersonalization
 constant CRH_IVK BlakePersonalization
 constant NOTE_COMMIT PedersenPersonalization
-{% for i in range(4) %}
+{% for i in range(32) %}
     constant MERKLE_{{ i }} PedersenPersonalization
 {% endfor %}
 
@@ -18,7 +18,7 @@ contract spend_contract
     param randomness_coin Fr
     param secret Fr
 
-{% for i in range(4) %}
+{% for i in range(32) %}
     param branch_{{ i }} Scalar
     param is_right_{{ i }} Bool
 {% endfor %}
@@ -113,7 +113,7 @@ start
     ec_get_u current cm
 
     # Our merkle tree has a height of 4
-{% for i in range(4) %}
+{% for i in range(32) %}
     # left = current
     # right = branch[{{ i }}]
     alloc_scalar branch param:branch_{{ i }}

src/crypto/merkle_node.rs

@@ -9,7 +9,7 @@ use crate::impl_vec;
 use crate::serial::{Decodable, Encodable, VarInt};
 use crate::{Error, Result};
 
-pub const SAPLING_COMMITMENT_TREE_DEPTH: usize = 6;
+pub const SAPLING_COMMITMENT_TREE_DEPTH: usize = 32;
 
 /// Compute a parent node in the Sapling commitment tree given its two children.
 pub fn merkle_hash(depth: usize, lhs: &[u8; 32], rhs: &[u8; 32]) -> bls12_381::Scalar {