diff --git a/risc0-selective-privacy-poc/core/src/account.rs b/risc0-selective-privacy-poc/core/src/account.rs
index 7bf9c5a..1c0b67b 100644
--- a/risc0-selective-privacy-poc/core/src/account.rs
+++ b/risc0-selective-privacy-poc/core/src/account.rs
@@ -5,17 +5,21 @@ use risc0_zkvm::{
 use serde::{Deserialize, Serialize};
 
 pub type Commitment = u32;
+pub type Nullifier = [u32; 8];
+pub type Address = [u32; 8];
+pub type Nonce = [u32; 8];
+pub type Key = [u32; 8];
 
 #[derive(Clone, Debug, Serialize, Deserialize, PartialEq, Eq)]
 pub struct Account {
-    pub address: [u32; 8],
+    pub address: Address,
     pub balance: u128,
-    pub nonce: [u32; 8],
+    pub nonce: Nonce,
 }
 
 impl Account {
     /// Creates a new account with address = hash(private_key) and balance = 0
-    pub fn new_from_private_key(private_key: [u32; 8], nonce: [u32; 8]) -> Self {
+    pub fn new_from_private_key(private_key: Address, nonce: Nonce) -> Self {
         let address = hash(&private_key);
         Self {
             address,
@@ -24,7 +28,7 @@ impl Account {
         }
     }
 
-    pub fn new(address: [u32; 8], nonce: [u32; 8]) -> Self {
+    pub fn new(address: Address, nonce: Nonce) -> Self {
         Self {
             address,
             balance: 0,
@@ -48,7 +52,7 @@ pub fn is_in_commitment_tree(_commitment: Commitment, _tree_root: [u32; 8]) -> b
 }
 
 /// Returns Hash(Commitment || private_key)
-pub fn compute_nullifier(commitment: &Commitment, private_key: &[u32; 8]) -> [u32; 8] {
+pub fn compute_nullifier(commitment: &Commitment, private_key: &Key) -> Nullifier {
     let mut bytes_to_hash = [0; 9]; // <- 1 word for the commitment, 8 words for the private key
     bytes_to_hash[..1].copy_from_slice(&[*commitment]);
     bytes_to_hash[1..].copy_from_slice(private_key);
diff --git a/risc0-selective-privacy-poc/core/src/input.rs b/risc0-selective-privacy-poc/core/src/input.rs
index 61809a5..9c303f0 100644
--- a/risc0-selective-privacy-poc/core/src/input.rs
+++ b/risc0-selective-privacy-poc/core/src/input.rs
@@ -1,12 +1,10 @@
+use crate::account::Key;
 use serde::{Deserialize, Serialize};
 
-pub type PrivateKey = [u32; 8];
-
 #[derive(Serialize, Deserialize)]
 pub enum InputVisibiility {
     // A public account
     Public,
     // A private account
-    Private(Option<PrivateKey>),
+    Private(Option<Key>),
 }
-
diff --git a/risc0-selective-privacy-poc/outer_methods/guest/src/bin/outer.rs b/risc0-selective-privacy-poc/outer_methods/guest/src/bin/outer.rs
index cc93293..c64a3f6 100644
--- a/risc0-selective-privacy-poc/outer_methods/guest/src/bin/outer.rs
+++ b/risc0-selective-privacy-poc/outer_methods/guest/src/bin/outer.rs
@@ -1,6 +1,6 @@
 use risc0_zkvm::{guest::env, serde::to_vec};
 use toy_example_core::{
-    account::{compute_nullifier, hash, is_in_commitment_tree, Account},
+    account::{compute_nullifier, hash, is_in_commitment_tree, Account, Nonce},
     input::InputVisibiility,
 };
 
@@ -30,7 +30,7 @@ fn main() {
     assert_eq!(input_visibilities.len() as u32, num_inputs);
 
     // Read nonces for outputs
-    let output_nonces: Vec<[u32; 8]> = env::read();
+    let output_nonces: Vec<Nonce> = env::read();
     assert_eq!(output_nonces.len() as u32, num_inputs);
 
     let commitment_tree_root: [u32; 8] = env::read();
diff --git a/risc0-selective-privacy-poc/src/private_execution.rs b/risc0-selective-privacy-poc/src/private_execution.rs
index fae0ed6..c41c1a4 100644
--- a/risc0-selective-privacy-poc/src/private_execution.rs
+++ b/risc0-selective-privacy-poc/src/private_execution.rs
@@ -2,19 +2,19 @@ use outer_methods::{OUTER_ELF, OUTER_ID};
 use rand::{rngs::OsRng, Rng};
 use risc0_zkvm::{default_prover, ExecutorEnv, Receipt};
 use toy_example_core::{
-    account::{Account, Commitment},
+    account::{Account, Address, Commitment, Nonce, Nullifier},
     input::InputVisibiility,
 };
 use transfer_methods::{TRANSFER_ELF, TRANSFER_ID};
 
 const COMMITMENT_TREE_ROOT: [u32; 8] = [0xdd, 0xee, 0xaa, 0xdd, 0xbb, 0xee, 0xee, 0xff];
 
-pub fn new_random_nonce() -> [u32; 8] {
+pub fn new_random_nonce() -> Nonce {
     let mut rng = OsRng;
     std::array::from_fn(|_| rng.gen())
 }
 
-fn mint_fresh_account(address: [u32; 8]) -> Account {
+fn mint_fresh_account(address: Address) -> Account {
     let nonce = new_random_nonce();
     Account::new(address, nonce)
 }
@@ -25,7 +25,7 @@ fn mint_fresh_account(address: [u32; 8]) -> Account {
 fn run_private_execution_of_transfer_program() {
     // This is supposed to be an existing private account (UTXO) with balance equal to 150.
     // And it is supposed to be a private account of the user running this private execution (hence the access to the private key)
-    let sender_private_key = [0; 8];
+    let sender_private_key = [1, 2, 3, 4, 4, 3, 2, 1];
     let sender = {
         // Creating it now but it's supposed to be already created by other previous transactions.
         let mut account = Account::new_from_private_key(sender_private_key, [1; 8]);
@@ -75,7 +75,7 @@ fn run_private_execution_of_transfer_program() {
     // Sanity check
     receipt.verify(OUTER_ID).unwrap();
 
-    let output: (Vec<Account>, Vec<[u32; 8]>, Vec<Commitment>) = receipt.journal.decode().unwrap();
+    let output: (Vec<Account>, Vec<Nullifier>, Vec<Commitment>) = receipt.journal.decode().unwrap();
     println!("public_outputs: {:?}", output.0);
     println!("nullifiers: {:?}", output.1);
     println!("commitments: {:?}", output.2);