if credElements[3] != "aws4_request" {
		return ch, ErrInvalidRequestVersion
	}
	cred.scope.request = credElements[3]
	return cred, ErrNone
}

// Parse signature from signature tag.
func parseSignature(signElement string) (string, APIErrorCode) {
	signFields := strings.Split(strings.TrimSpace(signElement), "=")
	if len(signFields) != 2 {
		return "", ErrMissingFields
	}
	if signFields[0] != "Signature" {