diff --git a/src/v4/aliyun_util.rs b/src/v4/aliyun_util.rs
index f408308..48755bd 100644
--- a/src/v4/aliyun_util.rs
+++ b/src/v4/aliyun_util.rs
@@ -94,7 +94,7 @@ pub fn add_common_headers(request: &mut Request) {
     }
 }
 
-fn get_timestamp() -> (String, String) {
+pub fn get_timestamp() -> (String, String) {
     let ymd_format = "yyyyMMdd";
     let ymd_hms_format = "yyyy-MM-dd'T'HH:mm:ss'Z'";
     let now = simpledateformat::get_utc_now();
@@ -103,14 +103,14 @@ fn get_timestamp() -> (String, String) {
     (ymd, ymd_hms)
 }
 
-fn digest_request_body(sign_algorithm: &SignAlgorithm, body: &Option<Vec<u8>>) -> String {
+pub fn digest_request_body(sign_algorithm: &SignAlgorithm, body: &Option<Vec<u8>>) -> String {
     match body {
         None => sign_algorithm.digest(&vec![]),
         Some(body) => sign_algorithm.digest(body),
     }
 }
 
-fn get_host(endpoint: &str) -> String {
+pub fn get_host(endpoint: &str) -> String {
     let lower_endpoint = endpoint.to_ascii_lowercase();
     let skip_chars = if lower_endpoint.starts_with("http://") {
         7
@@ -124,7 +124,7 @@ fn get_host(endpoint: &str) -> String {
     lower_endpoint.chars().skip(skip_chars).take_while(|c| *c != '/').collect()
 }
 
-fn get_nonce() -> String {
+pub fn get_nonce() -> String {
     let seq = SEQ.fetch_add(1, Ordering::Relaxed);
     let now = SystemTime::now();
     let rand_bytes: [u8; 32] = random();
@@ -133,14 +133,14 @@ fn get_nonce() -> String {
     "nonce-".to_string() + &secs_hex + "-" + &SignAlgorithm::Sha256.digest(seed.as_bytes())[0..32]
 }
 
-fn get_authorization(sign_algorithm: &SignAlgorithm,
-                     access_key: &DerivedAccessKey,
-                     date: &str, region: &str, product: &str,
-                     pathname: &str,
-                     method: &str,
-                     query: &BTreeMap<String, String>,
-                     headers: &BTreeMap<String, String>,
-                     payload: &str) -> String {
+pub fn get_authorization(sign_algorithm: &SignAlgorithm,
+                         access_key: &DerivedAccessKey,
+                         date: &str, region: &str, product: &str,
+                         pathname: &str,
+                         method: &str,
+                         query: &BTreeMap<String, String>,
+                         headers: &BTreeMap<String, String>,
+                         payload: &str) -> String {
     let signature = get_signature(sign_algorithm, &access_key.derived_access_key_secret,
                                   pathname, method, query, headers, payload);
     let signed_headers_str = get_signed_headers(headers).iter().map(|(k, _)| k.as_str()).collect::<Vec<_>>().join(";");
@@ -162,13 +162,13 @@ fn get_authorization(sign_algorithm: &SignAlgorithm,
     authorization
 }
 
-fn get_signature(sign_algorithm: &SignAlgorithm,
-                 signing_key: &[u8],
-                 pathname: &str,
-                 method: &str,
-                 query: &BTreeMap<String, String>,
-                 headers: &BTreeMap<String, String>,
-                 payload: &str) -> String {
+pub fn get_signature(sign_algorithm: &SignAlgorithm,
+                     signing_key: &[u8],
+                     pathname: &str,
+                     method: &str,
+                     query: &BTreeMap<String, String>,
+                     headers: &BTreeMap<String, String>,
+                     payload: &str) -> String {
     let canonical_uri = if pathname.is_empty() { "/" } else { pathname };
     let canonicalized_resource = build_canonicalized_resource(query);
     let canonicalized_headers = build_canonicalized_headers(headers);
@@ -196,7 +196,7 @@ fn get_signature(sign_algorithm: &SignAlgorithm,
     hex::encode(sign_algorithm.hmac_sign(string_to_sign.as_bytes(), signing_key))
 }
 
-fn get_signing_key(sign_algorithm: &SignAlgorithm, secret: &str, date: &str, region: &str, product: &str) -> Vec<u8> {
+pub fn get_signing_key(sign_algorithm: &SignAlgorithm, secret: &str, date: &str, region: &str, product: &str) -> Vec<u8> {
     let sc1 = join_slices(ALIYUN_V4.as_bytes(), secret.as_bytes());
     let sc2 = sign_algorithm.hmac_sign(date.as_bytes(), &sc1);
     let sc3 = sign_algorithm.hmac_sign(region.as_bytes(), &sc2);
@@ -204,7 +204,7 @@ fn get_signing_key(sign_algorithm: &SignAlgorithm, secret: &str, date: &str, reg
     sign_algorithm.hmac_sign(ALIYUN_V4_REQUEST.as_bytes(), &sc4)
 }
 
-fn get_region(product: &str, endpoint: &str) -> String {
+pub fn get_region(product: &str, endpoint: &str) -> String {
     if product.is_empty() || endpoint.is_empty() {
         return REGION_CENTER.into();
     }
@@ -216,7 +216,7 @@ fn get_region(product: &str, endpoint: &str) -> String {
     if region.is_empty() { REGION_CENTER.into() } else { region }
 }
 
-fn build_canonicalized_resource(query: &BTreeMap<String, String>) -> String {
+pub fn build_canonicalized_resource(query: &BTreeMap<String, String>) -> String {
     let mut canonicalized_resources = Vec::with_capacity(query.len());
     for (key, value) in query {
         let mut resource = String::with_capacity(key.len() + 1 + value.len());
@@ -242,7 +242,7 @@ fn build_canonicalized_headers(headers: &BTreeMap<String, String>) -> String {
     canonicalized_headers
 }
 
-fn get_signed_headers(headers: &BTreeMap<String, String>) -> Vec<(String, &String)> {
+pub fn get_signed_headers(headers: &BTreeMap<String, String>) -> Vec<(String, &String)> {
     let mut signed_headers = Vec::with_capacity(headers.len());
     for (key, value) in headers {
         let lower_key = key.to_lowercase();