diff --git a/pkg/sigv4/sigv4.go b/pkg/sigv4/sigv4.go
index 2d0429a..5829c40 100644
--- a/pkg/sigv4/sigv4.go
+++ b/pkg/sigv4/sigv4.go
@@ -15,19 +15,19 @@ import (
 	"time"
 )
 
-type Signer interface {
-	Sign(req *http.Request) error
+type signer interface {
+	sign(req *http.Request) error
 }
 
-type DefaultSigner struct {
+type defaultSigner struct {
 	config *Config
 
 	// noEscape represents the characters that AWS doesn't escape
 	noEscape [256]bool
 }
 
-func NewDefaultSigner(config *Config) Signer {
-	ds := &DefaultSigner{
+func newDefaultSigner(config *Config) signer {
+	ds := &defaultSigner{
 		config:   config,
 		noEscape: buildAwsNoEscape(),
 	}
@@ -35,7 +35,7 @@ func NewDefaultSigner(config *Config) Signer {
 	return ds
 }
 
-func (d *DefaultSigner) Sign(req *http.Request) error {
+func (d *defaultSigner) sign(req *http.Request) error {
 	now := time.Now().UTC()
 	iSO8601Date := now.Format(timeFormat)
 
@@ -81,7 +81,7 @@ func (d *DefaultSigner) Sign(req *http.Request) error {
 	return nil
 }
 
-func (d *DefaultSigner) getPayloadHash(req *http.Request) (string, error) {
+func (d *defaultSigner) getPayloadHash(req *http.Request) (string, error) {
 	if req.Body == nil {
 		return emptyStringSHA256, nil
 	}
diff --git a/pkg/sigv4/tripper.go b/pkg/sigv4/tripper.go
index ddc6e75..f7ed9cc 100644
--- a/pkg/sigv4/tripper.go
+++ b/pkg/sigv4/tripper.go
@@ -8,7 +8,7 @@ import (
 
 type Tripper struct {
 	config *Config
-	signer Signer
+	signer signer
 	next   http.RoundTripper
 }
 
@@ -42,13 +42,13 @@ func NewRoundTripper(config *Config, next http.RoundTripper) (*Tripper, error) {
 	tripper := &Tripper{
 		config: config,
 		next:   next,
-		signer: NewDefaultSigner(config),
+		signer: newDefaultSigner(config),
 	}
 	return tripper, nil
 }
 
 func (c *Tripper) RoundTrip(req *http.Request) (*http.Response, error) {
-	if err := c.signer.Sign(req); err != nil {
+	if err := c.signer.sign(req); err != nil {
 		return nil, err
 	}
 	return c.next.RoundTrip(req)