diff --git a/crypto/subtle.go b/crypto/subtle.go
index eca3c30..9a3f078 100644
--- a/crypto/subtle.go
+++ b/crypto/subtle.go
@@ -25,7 +25,7 @@ func DecryptWithoutIntegrity(key, input, iv []byte) ([]byte, error) {
 	return EncryptWithoutIntegrity(key, input, iv)
 }
 
-// DeriveKey derives a key from a password using scrypt.
-func DeriveKey(password string, salt []byte) ([]byte, error) {
-	return scrypt.Key([]byte(password), salt, 32768, 8, 1, 32)
+// DeriveKey derives a key from a password using scrypt. N should be set to the highest power of 2 you can derive within 100 milliseconds.
+func DeriveKey(password string, salt []byte, N int) ([]byte, error) {
+	return scrypt.Key([]byte(password), salt, N, 8, 1, 32)
 }
diff --git a/crypto/subtle_test.go b/crypto/subtle_test.go
index 1c8cbc7..06455dc 100644
--- a/crypto/subtle_test.go
+++ b/crypto/subtle_test.go
@@ -29,7 +29,7 @@ func TestSubtle_DecryptWithoutIntegrity(t *testing.T) {
 
 func TestSubtle_DeriveKey(t *testing.T) {
 	salt, _ := hex.DecodeString("c828f258a76aad7b")
-	dk, _ := DeriveKey("some password", salt)
+	dk, _ := DeriveKey("some password", salt, 32768)
 	if hex.EncodeToString(dk) != "9469cccfc8a8d005247f39fa3e5b35a97db456cecf18deac6d84364d0818d763" {
 		t.Fatal("DeriveKey returned unexpected result")
 	}