You can use DTLS, which is the secure protocol to be used with the UDP protocol and CoAP.

Thankyou Cristian but

i am already aware of it but any other solution other then DTLS or somehow like DTLS?

Hi Muhammad,

You can check this publication: Lithe: Lightweight Secure CoAP for the Internet of Things.

The authors proposed a novel DTLS header compression method to reduce the energy consumption by leveraging the 6LoWPAN standard

It can be found here:

https://ieeexplore.ieee.org/abstract/document/6576185/

Regards,

Elie Kfoury.