The new technological approaches bring us into the digital era, where data security is a part of our everyday lives. Nowadays cryptographic algorithms, which are also recommended by international security standards, are often developed for non-limited devices and they are not suitable for limited environments. This paper deals with a lightweight solution for the structure of big numbers, which should help with ordinary recommended cryptographic algorithms in limited devices. We introduce our lightweight structure and elementary algebra for cryptographic primitives based on non-limited OpenSSL library. Last but not least, we provide experimental measurements and verification on the real scenarios. © 2017 IEEE.