diff --git a/bindings/cashu-sdk-ffi/src/cashu_sdk.udl b/bindings/cashu-sdk-ffi/src/cashu_sdk.udl
index 4e2e8f1a..5d5e36c4 100644
--- a/bindings/cashu-sdk-ffi/src/cashu_sdk.udl
+++ b/bindings/cashu-sdk-ffi/src/cashu_sdk.udl
@@ -31,6 +31,11 @@ interface Secret {
 	sequence<u8> as_bytes();	
 };
 
+interface Id {
+    [Throws=CashuError]
+	constructor(string id);
+};
+
 interface PublicKey {
     [Throws=CashuError, Name=from_hex]
     constructor(string hex);
@@ -51,26 +56,26 @@ interface BlindedMessage {
 };
 
 interface Proof {
-	constructor(Amount amount, Secret secret, PublicKey c, string? id);
+	constructor(Amount amount, Secret secret, PublicKey c, Id? id);
 	Amount amount();
 	Secret secret();
 	PublicKey c();
-	string? id();
+	Id? id();
 };
 
 interface BlindedSignature {
-	constructor(string id, Amount amount, PublicKey c);
-	string id();
+	constructor(Id id, Amount amount, PublicKey c);
+	Id id();
 	Amount amount();
 	PublicKey c();
 };
 
 interface MintProof {
-	constructor(Amount? amount, Secret secret, PublicKey? c, string? id);
+	constructor(Amount? amount, Secret secret, PublicKey? c, Id? id);
 	Amount? amount();
 	Secret secret();
 	PublicKey? c();
-	string? id();
+	Id? id();
 	
 };
 
@@ -119,8 +124,8 @@ interface Keys {
 };
 
 interface KeySet {
-	constructor(string id, Keys keys);
-	string id();
+	constructor(Id id, Keys keys);
+	Id id();
 	Keys keys();
 };
 
@@ -131,8 +136,8 @@ interface MintKeySet {
 };
 
 interface KeySetResponse {
-	constructor(sequence<string> keyset_ids);
-	sequence<string> keyset_ids();
+	constructor(sequence<Id> keyset_ids);
+	sequence<Id> keyset_ids();
 };
 
 interface RequestMintResponse {
@@ -319,11 +324,12 @@ interface Wallet {
 
 
 interface Mint {
+    [Throws=CashuSdkError]
 	constructor(string secret, string derivation_path, record<string, MintKeySet> inactive_keysets, sequence<Secret> spent_secrets, u8 max_order);
 	KeySet active_keyset_pubkeys();
 	KeySetResponse keysets();
 	MintKeySet active_keyset();
-	KeySet? keyset(string id);
+	KeySet? keyset(Id id);
     [Throws=CashuSdkError]
 	PostMintResponse process_mint_request(MintRequest mint_request);
     [Throws=CashuSdkError]
diff --git a/bindings/cashu-sdk-ffi/src/lib.rs b/bindings/cashu-sdk-ffi/src/lib.rs
index 0692df2d..792cac22 100644
--- a/bindings/cashu-sdk-ffi/src/lib.rs
+++ b/bindings/cashu-sdk-ffi/src/lib.rs
@@ -7,7 +7,7 @@ mod wallet;
 mod ffi {
     pub use cashu_ffi::{
         Amount, BlindedMessage, BlindedMessages, BlindedSignature, Bolt11Invoice, CashuError,
-        CheckFeesRequest, CheckFeesResponse, CheckSpendableRequest, CheckSpendableResponse,
+        CheckFeesRequest, CheckFeesResponse, CheckSpendableRequest, CheckSpendableResponse, Id,
         InvoiceStatus, KeyPair, KeySet, KeySetResponse, Keys, MeltRequest, MeltResponse, MintInfo,
         MintKeySet, MintProof, MintProofs, MintRequest, MintVersion, Nut05MeltRequest,
         Nut05MeltResponse, PostMintResponse, Proof, PublicKey, RequestMintResponse, Secret,
diff --git a/bindings/cashu-sdk-ffi/src/mint.rs b/bindings/cashu-sdk-ffi/src/mint.rs
index 9d73a563..81e157b1 100644
--- a/bindings/cashu-sdk-ffi/src/mint.rs
+++ b/bindings/cashu-sdk-ffi/src/mint.rs
@@ -6,9 +6,11 @@ use std::{
 
 use cashu_sdk::mint::Mint as MintSdk;
 
+use cashu_sdk::nuts::nut02::Id as IdSdk;
+
 use crate::error::Result;
 use cashu_ffi::{
-    Amount, CheckSpendableRequest, CheckSpendableResponse, KeySet, KeySetResponse, MeltRequest,
+    Amount, CheckSpendableRequest, CheckSpendableResponse, Id, KeySet, KeySetResponse, MeltRequest,
     MeltResponse, MintKeySet, MintRequest, PostMintResponse, Proof, Secret, SplitRequest,
     SplitResponse,
 };
@@ -24,7 +26,7 @@ impl Mint {
         inactive_keysets: HashMap<String, Arc<MintKeySet>>,
         spent_secrets: Vec<Arc<Secret>>,
         max_order: u8,
-    ) -> Self {
+    ) -> Result<Self> {
         let spent_secrets = spent_secrets
             .into_iter()
             .map(|s| s.as_ref().deref().clone())
@@ -32,10 +34,13 @@ impl Mint {
 
         let inactive_keysets = inactive_keysets
             .into_iter()
-            .map(|(k, v)| (k, v.as_ref().deref().clone()))
+            .flat_map(|(k, v)| {
+                let id = IdSdk::try_from_base64(&k);
+                id.map(|id| (id, v.as_ref().deref().clone()))
+            })
             .collect();
 
-        Self {
+        Ok(Self {
             inner: MintSdk::new(
                 &secret,
                 &derivation_path,
@@ -44,7 +49,7 @@ impl Mint {
                 max_order,
             )
             .into(),
-        }
+        })
     }
 
     pub fn active_keyset_pubkeys(&self) -> Arc<KeySet> {
@@ -59,7 +64,7 @@ impl Mint {
         Arc::new(self.inner.read().unwrap().active_keyset.clone().into())
     }
 
-    pub fn keyset(&self, id: String) -> Option<Arc<KeySet>> {
+    pub fn keyset(&self, id: Arc<Id>) -> Option<Arc<KeySet>> {
         self.inner
             .read()
             .unwrap()