diff --git a/core/types/shard_state.go b/core/types/shard_state.go
index a160bb454..4816c47ba 100644
--- a/core/types/shard_state.go
+++ b/core/types/shard_state.go
@@ -21,6 +21,11 @@ type ShardState []Committee
 // BlsPublicKey defines the bls public key
 type BlsPublicKey [96]byte
 
+// Hex returns the hex string of bls public key
+func (pk BlsPublicKey) Hex() string {
+	return hex.EncodeToString(pk[:])
+}
+
 // NodeID represents node id (BLS address).
 type NodeID struct {
 	EcdsaAddress string
@@ -34,11 +39,6 @@ type Committee struct {
 	NodeList []NodeID
 }
 
-// Hex returns the hex string of bls public key
-func (pk BlsPublicKey) Hex() string {
-	return hex.EncodeToString(pk[:])
-}
-
 // GetHashFromNodeList will sort the list, then use Keccak256 to hash the list
 // notice that the input nodeList will be modified (sorted)
 func GetHashFromNodeList(nodeList []NodeID) []byte {