}
	if length <= 0 {
		length = accessKeyMaxLen
	}
	if length < accessKeyMinLen {
		return "", errors.New("auth: access key length is too short")
	}

	key := make([]byte, length)
	if _, err := io.ReadFull(random, key); err != nil {
		return "", err
	}
	for i := range key {
		key[i] = alphaNumericTable[key[i]%alphaNumericTableLen]
	}
	return string(key), nil
}