diff --git a/multipart.go b/multipart.go
index d7322a7..e5e4ed8 100644
--- a/multipart.go
+++ b/multipart.go
@@ -58,7 +58,6 @@ func (mp *S3Multipart) AddPart(r io.Reader, size int64, md5sum []byte) error {
 	}
 
 	req.Header.Set("Content-Length", fmt.Sprintf("%d", size))
-	req.Header.Set("Host", req.URL.Host)
 	req.Header.Set("Content-Type", "application/octet-stream")
 	req.ContentLength = size
 
@@ -114,7 +113,6 @@ func (mp *S3Multipart) Complete(contentType string) error {
 	}
 
 	req.Header.Set("Content-Length", fmt.Sprintf("%d", len(xmlBody)))
-	req.Header.Set("Host", req.URL.Host)
 	req.Header.Set("Content-Type", contentType)
 	req.ContentLength = int64(len(xmlBody))
 
diff --git a/s3.go b/s3.go
index a32bdb9..f95d24f 100644
--- a/s3.go
+++ b/s3.go
@@ -2,9 +2,7 @@ package s3
 
 import (
 	"bytes"
-	"crypto/hmac"
 	"crypto/md5"
-	"crypto/sha1"
 	"encoding/base64"
 	"encoding/xml"
 	"fmt"
@@ -14,9 +12,12 @@ import (
 	"net/http"
 	"net/url"
 	"runtime"
-	"sort"
 	"strings"
 	"time"
+
+	"github.com/aws/aws-sdk-go/aws/credentials"
+	"github.com/aws/aws-sdk-go/aws/endpoints"
+	"github.com/aws/aws-sdk-go/aws/signer/v4"
 )
 
 // S3 provides a wrapper around your S3 credentials. It carries no other internal state
@@ -38,66 +39,32 @@ func NewS3(bucket, accessId, secret string) *S3 {
 	}
 }
 
-func (s3 *S3) signRequest(req *http.Request) {
-	amzHeaders := ""
-	resourceUrl, _ := url.Parse("/" + s3.bucket + req.URL.Path)
-	resource := resourceUrl.String()
-
-	/* Ugh, AWS requires us to order the parameters in a specific ordering for
-	 * signing. Makes sense, but is annoying because a map does not have a defined
-	 * ordering (and basically returns elements in a random order) -- so we have
-	 * to sort by hand */
-	query := req.URL.Query()
-	if len(query) > 0 {
-		keys := []string{}
-
-		for k := range query {
-			keys = append(keys, k)
-		}
-
-		sort.Strings(keys)
-
-		parts := []string{}
-
-		for _, key := range keys {
-			vals := query[key]
-
-			for _, val := range vals {
-				if val == "" {
-					parts = append(parts, url.QueryEscape(key))
-
-				} else {
-					part := fmt.Sprintf("%s=%s", url.QueryEscape(key), url.QueryEscape(val))
-					parts = append(parts, part)
-				}
-			}
-		}
-
-		req.URL.RawQuery = strings.Join(parts, "&")
-	}
-
-	if req.URL.RawQuery != "" {
-		resource += "?" + req.URL.RawQuery
+func (s4 *S3) signRequest(req *http.Request) (er error) {
+	signer := v4.Signer{
+		Credentials:            credentials.NewStaticCredentials(s4.accessId, s4.secret, ""),
+		DisableURIPathEscaping: true,
 	}
 
+	t := time.Now()
 	if req.Header.Get("Date") == "" {
-		req.Header.Set("Date", time.Now().Format(time.RFC1123))
+		req.Header.Set("Date", t.Format(time.RFC1123))
 	}
 
-	authStr := strings.Join([]string{
-		strings.TrimSpace(req.Method),
-		req.Header.Get("Content-MD5"),
-		req.Header.Get("Content-Type"),
-		req.Header.Get("Date"),
-		amzHeaders + resource,
-	}, "\n")
-
-	h := hmac.New(sha1.New, []byte(s3.secret))
-	h.Write([]byte(authStr))
+	var seeker io.ReadSeeker
+	if req.Body != nil {
+		seeker = bytes.NewReader(streamToByte(req.Body))
+	}
+	_, err := signer.Sign(req, seeker, "s3", endpoints.ApNortheast1RegionID, t)
+	if err != nil {
+		return er
+	}
+	return nil
+}
 
-	h64 := base64.StdEncoding.EncodeToString(h.Sum(nil))
-	auth := "AWS" + " " + s3.accessId + ":" + h64
-	req.Header.Set("Authorization", auth)
+func streamToByte(stream io.Reader) []byte {
+	buf := new(bytes.Buffer)
+	buf.ReadFrom(stream)
+	return buf.Bytes()
 }
 
 func (s3 *S3) resource(path string, values url.Values) string {
@@ -177,10 +144,12 @@ func (s3 *S3) Put(r io.Reader, size int64, path string, md5sum []byte, contentTy
 
 	req.Header.Set("Content-Type", contentType)
 	req.Header.Set("Content-Length", fmt.Sprintf("%d", size))
-	req.Header.Set("Host", req.URL.Host)
 	req.ContentLength = size
 
-	s3.signRequest(req)
+	er = s3.signRequest(req)
+	if er != nil {
+		return er
+	}
 
 	resp, er := http.DefaultClient.Do(req)
 	if er != nil {
@@ -211,7 +180,10 @@ func (s3 *S3) Get(path string) (io.ReadCloser, http.Header, error) {
 		return nil, http.Header{}, er
 	}
 
-	s3.signRequest(req)
+	er = s3.signRequest(req)
+	if er != nil {
+		return nil, http.Header{}, er
+	}
 
 	resp, er := http.DefaultClient.Do(req)
 	if er != nil {
@@ -241,7 +213,10 @@ func (s3 *S3) Head(path string) (http.Header, error) {
 		return http.Header{}, er
 	}
 
-	s3.signRequest(req)
+	er = s3.signRequest(req)
+	if er != nil {
+		return http.Header{}, er
+	}
 
 	resp, er := http.DefaultClient.Do(req)
 	if er != nil {
@@ -313,9 +288,10 @@ func (s3 *S3) StartMultipart(path string) (*S3Multipart, error) {
 		return nil, er
 	}
 
-	req.Header.Set("Host", req.URL.Host)
-
-	s3.signRequest(req)
+	er = s3.signRequest(req)
+	if er != nil {
+		return nil, er
+	}
 
 	resp, er := http.DefaultClient.Do(req)
 	if er != nil {