# UNDF: UNDF-2026-000001013
--- a/p2p/protocol/identify/id.go
+++ b/p2p/protocol/identify/id.go
@@ -698,22 +698,18 @@ func (ids *idService) getRecordBytes() []byte {

 // diff takes two slices of strings (a and b) and computes which elements were added and removed in b
 func diff(a, b []protocol.ID) (added, removed []protocol.ID) {
-	// This is O(n^2), but it's fine because the slices are small.
-	for _, x := range b {
-		var found bool
-		if slices.Contains(a, x) {
-			found = true
-		}
-		if !found {
+	aSet := make(map[protocol.ID]struct{}, len(a))
+	for _, x := range a {
+		aSet[x] = struct{}{}
+	}
+	bSet := make(map[protocol.ID]struct{}, len(b))
+	for _, x := range b {
+		bSet[x] = struct{}{}
+		if _, ok := aSet[x]; !ok {
 			added = append(added, x)
 		}
 	}
 	for _, x := range a {
-		var found bool
-		if slices.Contains(b, x) {
-			found = true
-		}
-		if !found {
+		if _, ok := bSet[x]; !ok {
 			removed = append(removed, x)
 		}
 	}