diff --git a/Cargo.toml b/Cargo.toml
index 88bef034e..3415610a8 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -110,3 +110,7 @@ opcodes = { workspace = true, features = ["data"] }
 tracing.workspace = true
 zint.workspace = true
 hex.workspace = true
+
+# [features]
+# default = [ "evm" ]
+# evm = [  ]
diff --git a/examples/erc20.rs b/examples/erc20.rs
index ff81a685c..35e6cb7e4 100644
--- a/examples/erc20.rs
+++ b/examples/erc20.rs
@@ -4,23 +4,26 @@
 
 extern crate zink;
 
-use zink::{Mapping, Storage};
+use zink::{
+    primitives::{Address, String32, U256},
+    Mapping, Storage,
+};
 
-#[zink::storage(u32)]
+#[zink::storage(String32)]
 pub struct Name;
 
-#[zink::storage(u32)]
+#[zink::storage(String32)]
 pub struct Symbol;
 
-#[zink::storage(u32)]
+#[zink::storage(U256)]
 pub struct TotalSupply;
 
-#[zink::storage(i32, i32)]
+#[zink::storage(Address, U256)]
 pub struct Balances;
 
 /// Get value from the storage.
 #[zink::external]
-pub fn init(name: u32, symbol: u32) {
+pub fn init(name: String32, symbol: String32) {
     Name::set(name);
     Symbol::set(symbol);
 }
@@ -31,6 +34,12 @@ pub fn decimals() -> u32 {
     8
 }
 
+fn _transfer(_from: Address, _to: Address) {
+    // TODO: check and reverts
+}
+
+fn _update(_from: Address) {}
+
 #[cfg(not(target_arch = "wasm32"))]
 fn main() {}
 
@@ -41,18 +50,23 @@ fn deploy() -> anyhow::Result<()> {
     let mut contract = Contract::search("erc20")?.compile()?;
 
     let mut evm = EVM::default();
-    let mut calldata: Vec<u8> = Default::default();
-    calldata.extend_from_slice(&42.to_bytes32());
-    calldata.extend_from_slice(&42.to_bytes32());
+    let name = "The Zink Language";
+    let symbol = "zink";
 
     // 1. deploy
     let info = evm.deploy(
         &contract
             .construct(
                 [
-                    (vec![0].try_into()?, vec![42].try_into()?),
-                    (vec![1].try_into()?, vec![42].try_into()?),
-                    (vec![2].try_into()?, vec![42].try_into()?),
+                    (Name::STORAGE_KEY.to_bytes32().into(), name.to_vec().into()),
+                    (
+                        Symbol::STORAGE_KEY.to_bytes32().into(),
+                        symbol.to_vec().into(),
+                    ),
+                    (
+                        TotalSupply::STORAGE_KEY.to_bytes32().into(),
+                        vec![42].try_into()?,
+                    ),
                 ]
                 .into_iter()
                 .collect(),
@@ -65,13 +79,13 @@ fn deploy() -> anyhow::Result<()> {
     let info = evm
         .calldata(&contract.encode(&[b"name()".to_vec()])?)
         .call(address)?;
-    assert_eq!(info.ret, 42u64.to_bytes32());
+    assert_eq!(info.ret, name.to_bytes32());
 
     // 3. get symbol
     let info = evm
         .calldata(&contract.encode(&[b"symbol()".to_vec()])?)
         .call(address)?;
-    assert_eq!(info.ret, 42u64.to_bytes32());
+    assert_eq!(info.ret, symbol.to_bytes32());
 
     // 3. get total supply
     let info = evm
diff --git a/zink/codegen/src/lib.rs b/zink/codegen/src/lib.rs
index b2edf79c1..431c2da3b 100644
--- a/zink/codegen/src/lib.rs
+++ b/zink/codegen/src/lib.rs
@@ -7,6 +7,7 @@ use syn::{parse_macro_input, Attribute, DeriveInput, ItemFn, ItemStruct};
 mod event;
 mod selector;
 mod storage;
+mod utils;
 
 /// Event logging interface
 ///
diff --git a/zink/codegen/src/storage.rs b/zink/codegen/src/storage.rs
index dad1b3c24..6ea312ac8 100644
--- a/zink/codegen/src/storage.rs
+++ b/zink/codegen/src/storage.rs
@@ -1,5 +1,6 @@
 extern crate proc_macro;
 
+use crate::utils::Bytes32;
 use heck::AsSnakeCase;
 use proc_macro::TokenStream;
 use proc_macro2::{Literal, Span, TokenTree};
@@ -47,8 +48,7 @@ impl Storage {
         let is = &self.target;
         let name = self.target.ident.clone();
         let slot = storage_slot(name.to_string());
-        let mut key = [0; 32];
-        key[28..].copy_from_slice(&slot.to_le_bytes());
+        let key = slot.to_bytes32();
 
         let keyl = Literal::byte_string(&key);
         let mut expanded = quote! {
@@ -98,7 +98,7 @@ impl Storage {
 
                     let mut seed = [0; 64];
                     seed[..32].copy_from_slice(&key.bytes32());
-                    seed[60..].copy_from_slice(&Self::STORAGE_SLOT.to_le_bytes());
+                    seed[60..].copy_from_slice(&Self::STORAGE_SLOT.bytes32());
                     zink::keccak256(&seed)
                 }
             }
@@ -140,7 +140,7 @@ impl Storage {
 
                     let mut seed = [0; 64];
                     seed[..32].copy_from_slice(&key1.bytes32());
-                    seed[60..].copy_from_slice(&Self::STORAGE_SLOT.to_le_bytes());
+                    seed[60..].copy_from_slice(&Self::STORAGE_SLOT.bytes32());
                     let skey1 = zink::keccak256(&seed);
                     seed[..32].copy_from_slice(&skey1);
                     seed[32..].copy_from_slice(&key2.bytes32());
diff --git a/zink/codegen/src/utils.rs b/zink/codegen/src/utils.rs
new file mode 100644
index 000000000..7ab578804
--- /dev/null
+++ b/zink/codegen/src/utils.rs
@@ -0,0 +1,121 @@
+//! Utils for bytes conversion.
+//!
+//! TODO: move this util to other library
+
+/// Trait for converting type to bytes32.
+pub trait Bytes32: Sized {
+    /// Convert type to the lowest significant bytes 32.
+    fn to_bytes32(&self) -> [u8; 32];
+
+    /// Convert type to vec of bytes.
+    fn to_vec(&self) -> Vec<u8> {
+        self.to_bytes32().to_vec()
+    }
+}
+
+/// Implement Bytes32 for types.
+macro_rules! impl_bytes32 {
+    ($($ty:ident),+) => {
+        $(
+            impl Bytes32 for $ty {
+                fn to_bytes32(&self) -> [u8; 32] {
+                    let mut bytes = [0u8; 32];
+                    let ls_bytes = {
+                        self.to_le_bytes()
+                            .into_iter()
+                            .rev()
+                            .skip_while(|b| *b == 0)
+                            .collect::<Vec<_>>()
+                            .into_iter()
+                            .rev()
+                            .collect::<Vec<_>>()
+                    };
+
+                    bytes[(32 - ls_bytes.len())..].copy_from_slice(&ls_bytes);
+                    bytes
+                }
+
+                fn to_vec(&self) -> Vec<u8> {
+                    self.to_le_bytes().to_vec()
+                }
+            }
+        )+
+    };
+}
+
+impl Bytes32 for Vec<u8> {
+    fn to_bytes32(&self) -> [u8; 32] {
+        let mut bytes = [0u8; 32];
+        bytes[(32 - self.len())..].copy_from_slice(self);
+        bytes
+    }
+
+    fn to_vec(&self) -> Vec<u8> {
+        self.clone()
+    }
+}
+
+impl Bytes32 for [u8; 20] {
+    fn to_bytes32(&self) -> [u8; 32] {
+        let mut bytes = [0u8; 32];
+        bytes[12..].copy_from_slice(self);
+        bytes
+    }
+}
+
+impl Bytes32 for [u8; 32] {
+    fn to_bytes32(&self) -> [u8; 32] {
+        *self
+    }
+
+    fn to_vec(&self) -> Vec<u8> {
+        self.as_ref().into()
+    }
+}
+
+impl Bytes32 for &[u8] {
+    fn to_bytes32(&self) -> [u8; 32] {
+        let mut bytes = [0u8; 32];
+        bytes[(32 - self.len())..].copy_from_slice(self);
+        bytes
+    }
+
+    fn to_vec(&self) -> Vec<u8> {
+        (*self).into()
+    }
+}
+
+impl Bytes32 for () {
+    fn to_bytes32(&self) -> [u8; 32] {
+        [0; 32]
+    }
+
+    fn to_vec(&self) -> Vec<u8> {
+        Default::default()
+    }
+}
+
+impl Bytes32 for &str {
+    fn to_bytes32(&self) -> [u8; 32] {
+        let mut bytes = [0u8; 32];
+        bytes[(32 - self.len())..].copy_from_slice(self.as_bytes());
+        bytes
+    }
+
+    fn to_vec(&self) -> Vec<u8> {
+        self.as_bytes().into()
+    }
+}
+
+impl Bytes32 for bool {
+    fn to_bytes32(&self) -> [u8; 32] {
+        let mut output = [0; 32];
+        if *self {
+            output[31] = 1;
+        }
+
+        output
+    }
+}
+
+impl_bytes32!(i8, u8, i16, u16, i32, u32, usize, i64, u64, i128, u128);
diff --git a/zink/src/ffi/asm.rs b/zink/src/ffi/asm.rs
index 77d88ec08..dceea900b 100644
--- a/zink/src/ffi/asm.rs
+++ b/zink/src/ffi/asm.rs
@@ -1,6 +1,6 @@
 //! Assembly FFI.
 
-use crate::primitives::Address;
+use crate::primitives::{Address, U256};
 
 #[link(wasm_import_module = "asm")]
 #[allow(improper_ctypes)]
@@ -32,6 +32,9 @@ extern "C" {
     /// Push address to stack
     pub fn push_address(address: Address);
 
+    /// Push u256 to stack
+    pub fn push_u256(u256: U256);
+
     /// Load a 8-bit signed integer from the storage.
     pub fn sload_i8() -> i8;
 
@@ -58,4 +61,7 @@ extern "C" {
 
     /// Load address from storage
     pub fn sload_address() -> Address;
+
+    /// Load address from storage
+    pub fn sload_u256() -> U256;
 }
diff --git a/zink/src/ffi/evm.rs b/zink/src/ffi/evm.rs
index 398ec523c..e2d2cdcaa 100644
--- a/zink/src/ffi/evm.rs
+++ b/zink/src/ffi/evm.rs
@@ -100,7 +100,7 @@ extern "C" {
     pub fn push31(val: i32);
 
     /// Push 32 bytes to the stack.
-    pub fn push32(val: i32);
+    pub fn push32();
 
     /// Store a value in the storage
     pub fn sstore();
diff --git a/zink/src/primitives/address.rs b/zink/src/primitives/address.rs
index be979b915..6df50fc27 100644
--- a/zink/src/primitives/address.rs
+++ b/zink/src/primitives/address.rs
@@ -9,6 +9,12 @@ pub struct Address(
 );
 
 impl Address {
+    /// Returns empty address
+    #[cfg(not(target_family = "wasm"))]
+    pub const fn empty() -> Self {
+        Address([0; 20])
+    }
+
     /// if self equal to another
     ///
     /// NOTE: not using core::cmp because it uses registers in wasm
diff --git a/zink/src/primitives/mod.rs b/zink/src/primitives/mod.rs
index d0f41fb0b..67b4af318 100644
--- a/zink/src/primitives/mod.rs
+++ b/zink/src/primitives/mod.rs
@@ -1,5 +1,11 @@
 //! Zink primitive types
 
 mod address;
+mod u256;
 
 pub use address::Address;
+pub use u256::U256;
+
+pub type Bytes20 = Address;
+pub type Bytes32 = U256;
+pub type String32 = U256;
diff --git a/zink/src/primitives/u256.rs b/zink/src/primitives/u256.rs
new file mode 100644
index 000000000..73ced9aca
--- /dev/null
+++ b/zink/src/primitives/u256.rs
@@ -0,0 +1,34 @@
+use crate::{ffi, storage::StorageValue, Asm};
+
+/// Account address
+#[repr(C)]
+#[derive(Clone, Copy)]
+pub struct U256(
+    #[cfg(target_family = "wasm")] i32,
+    #[cfg(not(target_family = "wasm"))] [u8; 32],
+);
+
+impl U256 {
+    /// Returns empty address
+    #[cfg(not(target_family = "wasm"))]
+    pub const fn empty() -> Self {
+        U256([0; 32])
+    }
+}
+
+impl Asm for U256 {
+    fn push(self) {
+        unsafe { ffi::asm::push_u256(self) }
+    }
+
+    #[cfg(not(target_family = "wasm"))]
+    fn bytes32(&self) -> [u8; 32] {
+        self.0
+    }
+}
+
+impl StorageValue for U256 {
+    fn sload() -> Self {
+        unsafe { ffi::asm::sload_u256() }
+    }
+}