diff --git a/src/api/dart_ffi.rs b/src/api/dart_ffi.rs
index fad148a..3d15234 100644
--- a/src/api/dart_ffi.rs
+++ b/src/api/dart_ffi.rs
@@ -637,7 +637,7 @@ pub async unsafe extern "C" fn sign(
     from_c_str!(tx_plan);
     let res = async {
         let tx_plan: TransactionPlan = serde_json::from_str(&tx_plan)?;
-        let raw_tx = crate::api::payment_v2::sign_plan(coin, account, &tx_plan)?;
+        let raw_tx = crate::api::payment_v2::sign_plan(coin, account, &tx_plan, false)?;
         let tx_str = base64::encode(&raw_tx);
         Ok::<_, anyhow::Error>(tx_str)
     };
diff --git a/src/api/payment_v2.rs b/src/api/payment_v2.rs
index c18f65b..4ec5d54 100644
--- a/src/api/payment_v2.rs
+++ b/src/api/payment_v2.rs
@@ -122,7 +122,7 @@ pub async fn build_tx_plan(
     Ok(tx_plan)
 }
 
-pub fn sign_plan(coin: u8, account: u32, tx_plan: &TransactionPlan) -> anyhow::Result<Vec<u8>> {
+pub fn sign_plan(coin: u8, account: u32, tx_plan: &TransactionPlan, frost: bool) -> anyhow::Result<Vec<u8>> {
     let c = CoinConfig::get(coin);
     let network = c.chain.network();
     let fvk = {
@@ -146,7 +146,7 @@ pub fn sign_plan(coin: u8, account: u32, tx_plan: &TransactionPlan) -> anyhow::R
     }
 
     let keys = get_secret_keys(coin, account)?;
-    let tx = build_tx(c.chain.network(), &keys, &tx_plan, OsRng)?;
+    let tx = build_tx(c.chain.network(), &keys, &tx_plan, frost, OsRng)?;
     Ok(tx)
 }
 
@@ -155,7 +155,7 @@ pub async fn sign_and_broadcast(
     account: u32,
     tx_plan: &TransactionPlan,
 ) -> anyhow::Result<String> {
-    let tx = sign_plan(coin, account, tx_plan)?;
+    let tx = sign_plan(coin, account, tx_plan, false)?;
     let txid = broadcast_tx(&tx).await?;
     let id_notes: Vec<_> = tx_plan
         .spends
diff --git a/src/main/rpc.rs b/src/main/rpc.rs
index 5ec4a65..4805acc 100644
--- a/src/main/rpc.rs
+++ b/src/main/rpc.rs
@@ -349,7 +349,7 @@ pub async fn build_from_plan(tx_plan: Json<TransactionPlan>) -> Result<String, E
     }
 
     let keys = get_secret_keys(c.coin, c.id_account)?;
-    let tx = build_tx(c.chain.network(), &keys, &tx_plan, OsRng).unwrap();
+    let tx = build_tx(c.chain.network(), &keys, &tx_plan, false, OsRng).unwrap();
     let tx = hex::encode(&tx);
     Ok(tx)
 }
diff --git a/src/main/sign.rs b/src/main/sign.rs
index 448fa8b..29003f4 100644
--- a/src/main/sign.rs
+++ b/src/main/sign.rs
@@ -88,7 +88,7 @@ fn main() -> anyhow::Result<()> {
         orchard: orchard_sk,
     };
 
-    let tx = build_tx(&network, &keys, &tx_plan, OsRng)?;
+    let tx = build_tx(&network, &keys, &tx_plan, true, OsRng)?;
 
     fs::write(out_filename, hex::encode(&tx))?;
     Ok(())
diff --git a/src/note_selection/builder.rs b/src/note_selection/builder.rs
index df63cc5..6807b65 100644
--- a/src/note_selection/builder.rs
+++ b/src/note_selection/builder.rs
@@ -11,6 +11,7 @@ use orchard::builder::Builder as OrchardBuilder;
 use orchard::bundle::Flags;
 use orchard::keys::{FullViewingKey, Scope, SpendAuthorizingKey, SpendingKey};
 use orchard::note::Nullifier;
+use orchard::primitives::redpallas::{self, SpendAuth};
 use orchard::value::NoteValue;
 use orchard::{Address, Anchor, Bundle};
 use rand::{CryptoRng, RngCore};
@@ -72,6 +73,7 @@ pub fn build_tx(
     network: &Network,
     skeys: &SecretKeys,
     plan: &TransactionPlan,
+    frost: bool,
     mut rng: impl RngCore + CryptoRng + Clone,
 ) -> anyhow::Result<Vec<u8>> {
     let secp = Secp256k1::<All>::new();
@@ -251,6 +253,10 @@ pub fn build_tx(
     let sig_hash = signature_hash(&unauthed_tx, &SignableInput::Shielded, &txid_parts);
     let sig_hash: [u8; 32] = sig_hash.as_ref().clone();
 
+    if frost {
+        println!("SIGHASH: {}", hex::encode(&sig_hash));
+    }
+
     let transparent_bundle = unauthed_tx
         .transparent_bundle()
         .map(|tb| tb.clone().apply_signatures(&unauthed_tx, &txid_parts));
@@ -272,9 +278,26 @@ pub fn build_tx(
             .clone()
             .create_proof(get_proving_key(), &mut rng)
             .unwrap();
-        proven
-            .apply_signatures(&mut rng, sig_hash, &orchard_signing_keys)
-            .unwrap()
+        if frost {
+            let mut buffer = String::new();
+            let stdin = std::io::stdin();
+            println!("Input hex-encoded signature: ");
+            stdin.read_line(&mut buffer).unwrap();
+            let signature = hex::decode(buffer.trim()).unwrap();
+            let signature: [u8; 64] = signature.try_into().unwrap();
+            let signature = redpallas::Signature::<SpendAuth>::from(signature);
+
+            proven
+                .prepare(&mut rng, sig_hash)
+                .append_signatures(&[signature])
+                .unwrap()
+                .finalize()
+                .unwrap()
+        } else {
+            proven
+                .apply_signatures(&mut rng, sig_hash, &orchard_signing_keys)
+                .unwrap()
+        }
     });
 
     let tx_data: TransactionData<zcash_primitives::transaction::Authorized> =
diff --git a/src/taddr.rs b/src/taddr.rs
index 3f8105a..f7189e3 100644
--- a/src/taddr.rs
+++ b/src/taddr.rs
@@ -353,7 +353,7 @@ pub async fn sweep_tkey(
         orchard: None,
     };
     println!("build_tx");
-    let tx = build_tx(network, &skeys, &tx_plan, OsRng)?;
+    let tx = build_tx(network, &skeys, &tx_plan, false, OsRng)?;
     println!("broadcast_tx");
     let txid = broadcast_tx(&tx).await?;
     Ok(txid)