diff --git a/cosmwasm/contracts/wormchain-accounting/schema/wormchain-accounting.json b/cosmwasm/contracts/wormchain-accounting/schema/wormchain-accounting.json
index 4be6f5c40..b3cc0aa5c 100644
--- a/cosmwasm/contracts/wormchain-accounting/schema/wormchain-accounting.json
+++ b/cosmwasm/contracts/wormchain-accounting/schema/wormchain-accounting.json
@@ -705,10 +705,9 @@
               "$ref": "#/definitions/Observation"
             },
             "signatures": {
-              "type": "array",
-              "items": {
-                "$ref": "#/definitions/Signature"
-              }
+              "type": "integer",
+              "format": "uint128",
+              "minimum": 0.0
             }
           },
           "additionalProperties": false
@@ -806,31 +805,6 @@
           },
           "additionalProperties": false
         },
-        "Signature": {
-          "description": "Signatures are typical ECDSA signatures prefixed with a Guardian position. These have the following byte layout: ```markdown 0  .. 64: Signature   (ECDSA) 64 .. 65: Recovery ID (ECDSA) ```",
-          "type": "object",
-          "required": [
-            "index",
-            "signature"
-          ],
-          "properties": {
-            "index": {
-              "type": "integer",
-              "format": "uint8",
-              "minimum": 0.0
-            },
-            "signature": {
-              "type": "array",
-              "items": {
-                "type": "integer",
-                "format": "uint8",
-                "minimum": 0.0
-              },
-              "maxItems": 65,
-              "minItems": 65
-            }
-          }
-        },
         "TokenAddress": {
           "type": "string"
         }
@@ -997,10 +971,9 @@
               "$ref": "#/definitions/Observation"
             },
             "signatures": {
-              "type": "array",
-              "items": {
-                "$ref": "#/definitions/Signature"
-              }
+              "type": "integer",
+              "format": "uint128",
+              "minimum": 0.0
             }
           },
           "additionalProperties": false
@@ -1079,31 +1052,6 @@
           },
           "additionalProperties": false
         },
-        "Signature": {
-          "description": "Signatures are typical ECDSA signatures prefixed with a Guardian position. These have the following byte layout: ```markdown 0  .. 64: Signature   (ECDSA) 64 .. 65: Recovery ID (ECDSA) ```",
-          "type": "object",
-          "required": [
-            "index",
-            "signature"
-          ],
-          "properties": {
-            "index": {
-              "type": "integer",
-              "format": "uint8",
-              "minimum": 0.0
-            },
-            "signature": {
-              "type": "array",
-              "items": {
-                "type": "integer",
-                "format": "uint8",
-                "minimum": 0.0
-              },
-              "maxItems": 65,
-              "minItems": 65
-            }
-          }
-        },
         "TokenAddress": {
           "type": "string"
         },
@@ -1363,10 +1311,9 @@
               "$ref": "#/definitions/Observation"
             },
             "signatures": {
-              "type": "array",
-              "items": {
-                "$ref": "#/definitions/Signature"
-              }
+              "type": "integer",
+              "format": "uint128",
+              "minimum": 0.0
             }
           },
           "additionalProperties": false
@@ -1420,31 +1367,6 @@
             }
           },
           "additionalProperties": false
-        },
-        "Signature": {
-          "description": "Signatures are typical ECDSA signatures prefixed with a Guardian position. These have the following byte layout: ```markdown 0  .. 64: Signature   (ECDSA) 64 .. 65: Recovery ID (ECDSA) ```",
-          "type": "object",
-          "required": [
-            "index",
-            "signature"
-          ],
-          "properties": {
-            "index": {
-              "type": "integer",
-              "format": "uint8",
-              "minimum": 0.0
-            },
-            "signature": {
-              "type": "array",
-              "items": {
-                "type": "integer",
-                "format": "uint8",
-                "minimum": 0.0
-              },
-              "maxItems": 65,
-              "minItems": 65
-            }
-          }
         }
       }
     },
diff --git a/cosmwasm/contracts/wormchain-accounting/src/contract.rs b/cosmwasm/contracts/wormchain-accounting/src/contract.rs
index ad5a42783..e4302c265 100644
--- a/cosmwasm/contracts/wormchain-accounting/src/contract.rs
+++ b/cosmwasm/contracts/wormchain-accounting/src/contract.rs
@@ -109,11 +109,6 @@ fn submit_observations(
     let quorum = deps
         .querier
         .query::<u32>(&WormholeQuery::CalculateQuorum { guardian_set_index }.into())
-        .and_then(|q| {
-            usize::try_from(q).map_err(|_| StdError::ConversionOverflow {
-                source: ConversionOverflowError::new("u32", "usize", q.to_string()),
-            })
-        })
         .context("failed to calculate quorum")?;
 
     let observations: Vec<Observation> =
@@ -159,7 +154,7 @@ fn handle_observation(
     mut deps: DepsMut<WormholeQuery>,
     o: Observation,
     guardian_set_index: u32,
-    quorum: usize,
+    quorum: u32,
     sig: Signature,
 ) -> anyhow::Result<(ObservationStatus, Option<Event>)> {
     let digest_key = DIGESTS.key((o.emitter_chain, o.emitter_address.to_vec(), o.sequence));
@@ -194,9 +189,9 @@ fn handle_observation(
         }
     };
 
-    data.add_signature(sig)?;
+    data.add_signature(sig.index);
 
-    if data.signatures().len() < quorum {
+    if data.num_signatures() < quorum {
         // Still need more signatures so just save the pending transfer data and exit.
         key.save(deps.storage, &pending)
             .context("failed to save pending transfers")?;
diff --git a/cosmwasm/contracts/wormchain-accounting/src/state.rs b/cosmwasm/contracts/wormchain-accounting/src/state.rs
index bb05d2d4a..f1b4563eb 100644
--- a/cosmwasm/contracts/wormchain-accounting/src/state.rs
+++ b/cosmwasm/contracts/wormchain-accounting/src/state.rs
@@ -2,9 +2,7 @@ use accounting::state::transfer;
 use cosmwasm_schema::cw_serde;
 use cosmwasm_std::Binary;
 use cw_storage_plus::Map;
-use thiserror::Error;
 use tinyvec::TinyVec;
-use wormhole::vaa::Signature;
 
 use crate::msg::Observation;
 
@@ -18,18 +16,12 @@ pub struct PendingTransfer {
     pub data: Vec<Data>,
 }
 
-#[derive(Error, Debug)]
-#[error("cannot submit duplicate signatures for the same observation")]
-pub struct DuplicateSignatureError;
-
 #[cw_serde]
 #[derive(Default)]
 pub struct Data {
     observation: Observation,
-
     guardian_set_index: u32,
-
-    signatures: Vec<Signature>,
+    signatures: u128,
 }
 
 impl Data {
@@ -37,7 +29,7 @@ impl Data {
         Self {
             observation,
             guardian_set_index,
-            signatures: Vec::new(),
+            signatures: 0,
         }
     }
 
@@ -49,29 +41,69 @@ impl Data {
         self.guardian_set_index
     }
 
-    pub fn signatures(&self) -> &[Signature] {
-        &self.signatures
+    pub fn signatures(&self) -> u128 {
+        self.signatures
+    }
+
+    /// Returns the number of signatures for this `Data`.
+    pub fn num_signatures(&self) -> u32 {
+        self.signatures.count_ones()
     }
 
     /// Returns true if there is a signature associated with `index` in this `Data`.
     pub fn has_signature(&self, index: u8) -> bool {
-        self.signatures
-            .binary_search_by_key(&index, |s| s.index)
-            .is_ok()
+        assert!(index < 128);
+        self.signatures & (1u128 << index) != 0
     }
 
-    /// Adds `sig` to the list of signatures for this transfer data.  Returns true if `sig`
-    /// was successfully added or false if `sig` was already in the signature list.
-    pub fn add_signature(&mut self, sig: Signature) -> Result<(), DuplicateSignatureError> {
-        match self
-            .signatures
-            .binary_search_by_key(&sig.index, |s| s.index)
-        {
-            Ok(_) => Err(DuplicateSignatureError),
-            Err(idx) => {
-                self.signatures.insert(idx, sig);
-                Ok(())
-            }
+    /// Adds `sig` to the list of signatures for this `Data`.
+    pub fn add_signature(&mut self, index: u8) {
+        assert!(index < 128);
+        self.signatures |= 1u128 << index;
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    use std::panic::catch_unwind;
+
+    #[test]
+    fn add_signatures() {
+        let mut data = Data::default();
+        for i in 0..128 {
+            assert!(!data.has_signature(i));
+            data.add_signature(i);
+            assert!(data.has_signature(i));
+            assert_eq!(u32::from(i + 1), data.num_signatures());
+        }
+    }
+
+    #[test]
+    fn add_signatures_rev() {
+        let mut data = Data::default();
+        for i in (0..128).rev() {
+            assert!(!data.has_signature(i));
+            data.add_signature(i);
+            assert!(data.has_signature(i));
+            assert_eq!(u32::from(128 - i), data.num_signatures());
+        }
+    }
+
+    #[test]
+    fn has_out_of_bounds_signature() {
+        for i in 128..=u8::MAX {
+            catch_unwind(|| Data::default().has_signature(i))
+                .expect_err("successfully checked for out-of-bounds signature");
+        }
+    }
+
+    #[test]
+    fn add_out_of_bounds_signature() {
+        for i in 128..=u8::MAX {
+            catch_unwind(|| Data::default().add_signature(i))
+                .expect_err("successfully added out-of-bounds signature");
         }
     }
 }
diff --git a/cosmwasm/contracts/wormchain-accounting/tests/submit_observations.rs b/cosmwasm/contracts/wormchain-accounting/tests/submit_observations.rs
index 417dbad9a..99f26e09f 100644
--- a/cosmwasm/contracts/wormchain-accounting/tests/submit_observations.rs
+++ b/cosmwasm/contracts/wormchain-accounting/tests/submit_observations.rs
@@ -166,6 +166,8 @@ fn duplicates() {
 
     for (i, s) in signatures.into_iter().enumerate() {
         contract.submit_observations(obs.clone(), index, s).unwrap();
+        // Submitting a duplicate signature is not an error for pending transfers. Submitting any
+        // signature for a committed transfer is not an error as long as the digests match.
         let resp = contract.submit_observations(obs.clone(), index, s).unwrap();
         let status = from_binary::<Vec<SubmitObservationResponse>>(&resp.data.unwrap())
             .unwrap()
@@ -176,18 +178,9 @@ fn duplicates() {
             // Resubmitting the same signature without quorum will return an error.
             for o in &observations {
                 let key = transfer::Key::new(o.emitter_chain, o.emitter_address.into(), o.sequence);
-                if let ObservationStatus::Error(ref err) = status[&key] {
-                    assert!(err.contains("duplicate signatures"));
-                } else {
-                    panic!(
-                        "unexpected status for duplicate signature: {:?}",
-                        status[&key]
-                    );
-                }
+                assert!(matches!(status[&key], ObservationStatus::Pending));
             }
         } else {
-            // Submitting a signature for a committed transfer is not an error as long as the
-            // digests match.
             for o in &observations {
                 let key = transfer::Key::new(o.emitter_chain, o.emitter_address.into(), o.sequence);
                 assert!(matches!(status[&key], ObservationStatus::Committed));