diff --git a/emmarin/apps/swapvm/app/Cargo.toml b/emmarin/apps/swapvm/app/Cargo.toml
index 069b7d8..71b2f9e 100644
--- a/emmarin/apps/swapvm/app/Cargo.toml
+++ b/emmarin/apps/swapvm/app/Cargo.toml
@@ -4,6 +4,7 @@ version = "0.1.0"
 edition = "2021"
 
 [dependencies]
+rand = "0.8.5"
 cl = { path = "../../../cl/cl" }
 risc0-zkvm = "1.2"
-serde = { version = "1.0", features = ["derive"] }
\ No newline at end of file
+serde = { version = "1.0", features = ["derive"] }
diff --git a/emmarin/apps/swapvm/app/src/lib.rs b/emmarin/apps/swapvm/app/src/lib.rs
index c5bf27c..b7d4837 100644
--- a/emmarin/apps/swapvm/app/src/lib.rs
+++ b/emmarin/apps/swapvm/app/src/lib.rs
@@ -6,11 +6,76 @@ use cl::{
     },
     mantle::ZoneId,
 };
+use rand::RngCore;
 use risc0_zkvm::sha::rust_crypto::{Digest, Sha256};
 use serde::{Deserialize, Serialize};
 use std::collections::{BTreeMap, BTreeSet};
 
 const FUNDS_SK: NullifierSecret = NullifierSecret([0; 16]);
+pub const ZONE_ID: [u8; 32] = [128; 32];
+
+pub fn swap_goal_unit() -> UnitWitness {
+    UnitWitness::nop(b"SWAP")
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
+pub struct SwapOutput {
+    // value will be set at the market price
+    pub state: [u8; 32],
+    pub unit: Unit,
+    pub nonce: Nonce,
+    pub zone_id: ZoneId,
+    pub nf_pk: NullifierCommitment,
+}
+impl SwapOutput {
+    pub fn basic(
+        unit: Unit,
+        zone_id: ZoneId,
+        nf_pk: NullifierCommitment,
+        rng: impl RngCore,
+    ) -> Self {
+        Self {
+            state: [0; 32],
+            unit,
+            nonce: Nonce::random(rng),
+            zone_id,
+            nf_pk,
+        }
+    }
+}
+
+#[derive(Debug, Serialize, Deserialize)]
+pub struct SwapArgs {
+    // the user specifies the template forthe output note
+    pub output: SwapOutput,
+    // minimum value of the output note
+    pub limit: u64,
+}
+
+impl SwapArgs {
+    pub fn to_output(self, value: u64) -> OutputWitness {
+        assert!(value >= self.limit);
+        OutputWitness {
+            state: self.output.state,
+            value,
+            unit: self.output.unit,
+            nonce: self.output.nonce,
+            zone_id: self.output.zone_id,
+            nf_pk: self.output.nf_pk,
+        }
+    }
+}
+
+pub fn swap_goal_note(rng: impl RngCore) -> OutputWitness {
+    OutputWitness {
+        state: [0u8; 32],
+        value: 1,
+        unit: swap_goal_unit().unit(),
+        nonce: Nonce::random(rng),
+        zone_id: ZONE_ID,
+        nf_pk: NullifierSecret::zero().commit(),
+    }
+}
 
 // TODO: order pair tokens lexicographically
 fn get_pair_share_unit(pair: Pair) -> UnitWitness {
@@ -230,7 +295,7 @@ impl ZoneData {
             assert!(zone_update.has_output(&shares.note_commitment()));
         }
 
-        // TODO: chech shares have been burned
+        // TODO: check shares have been burned
     }
 
     pub fn expected_pool_balances(&self) -> BTreeMap<Unit, u64> {
diff --git a/emmarin/cl/cl/Cargo.toml b/emmarin/cl/cl/Cargo.toml
index a210628..45edc9d 100644
--- a/emmarin/cl/cl/Cargo.toml
+++ b/emmarin/cl/cl/Cargo.toml
@@ -9,6 +9,7 @@ rand_core = "0.6.0"
 hex = "0.4.3"
 risc0-zkvm = "1.2"
 itertools = "0.14"
+bincode = { version = "2", features = ["serde"] }
 
 [dev-dependencies]
 rand = "0.8.5"
diff --git a/emmarin/cl/cl/src/crust/balance.rs b/emmarin/cl/cl/src/crust/balance.rs
index 8de4ac6..c14eca6 100644
--- a/emmarin/cl/cl/src/crust/balance.rs
+++ b/emmarin/cl/cl/src/crust/balance.rs
@@ -14,6 +14,15 @@ pub struct UnitWitness {
 }
 
 impl UnitWitness {
+    pub fn nop(args: &[u8]) -> Self {
+        Self {
+            spending_covenant: NOP_COVENANT,
+            minting_covenant: NOP_COVENANT,
+            burning_covenant: NOP_COVENANT,
+            arg: crate::hash(args),
+        }
+    }
+
     pub fn unit(&self) -> Unit {
         let mut hasher = Hash::new();
         hasher.update(b"NOMOS_CL_UNIT");
diff --git a/emmarin/cl/cl/src/crust/tx.rs b/emmarin/cl/cl/src/crust/tx.rs
index c8904c5..31c0c7c 100644
--- a/emmarin/cl/cl/src/crust/tx.rs
+++ b/emmarin/cl/cl/src/crust/tx.rs
@@ -113,8 +113,9 @@ impl TxWitness {
         self
     }
 
-    pub fn add_output(mut self, output: OutputWitness, data: Vec<u8>) -> Self {
-        self.outputs.push((output, data));
+    pub fn add_output(mut self, output: OutputWitness, data: impl Serialize) -> Self {
+        self.outputs.push((output, crate::serialize(data)));
+
         self
     }
 
diff --git a/emmarin/cl/cl/src/lib.rs b/emmarin/cl/cl/src/lib.rs
index 923997a..1932417 100644
--- a/emmarin/cl/cl/src/lib.rs
+++ b/emmarin/cl/cl/src/lib.rs
@@ -3,6 +3,7 @@ pub mod ds;
 pub mod mantle;
 
 pub use risc0_zkvm::sha::rust_crypto::{Digest, Sha256};
+use serde::{de::DeserializeOwned, Serialize};
 
 pub type Hash = Sha256;
 
@@ -11,3 +12,15 @@ pub fn hash(data: &[u8]) -> [u8; 32] {
     hasher.update(data);
     hasher.finalize().into()
 }
+
+// TODO: spec serializiation
+pub fn serialize(data: impl Serialize) -> Vec<u8> {
+    bincode::serde::encode_to_vec(data, bincode::config::standard()).unwrap()
+}
+
+pub fn deserialize<T: DeserializeOwned>(bytes: &[u8]) -> T {
+    let (value, bytes_read) = bincode::serde::decode_from_slice(bytes, bincode::config::standard())
+        .expect("failed to deserialize");
+    assert_eq!(bytes_read, bytes.len());
+    value
+}