Lightweight cryptography is an encryption strategy that provides small features of footprints to assure security during communication. It intends to expand the cryptography applications to the resource-limited IoT environment. The lightweight cryptography is highly motivated for CoAP enabled IoT environment. The main motivations behind lightweight cryptography are occupying less memory, minimum computing resources, less battery power, and high speed to perform the cryptography based key exchanging and security functions.
   In lightweight cryptography, the block and key lengths are shorter than the normal cryptography. Lightweight cryptography offers a sufficient level of security by using modernized key exchanging algorithms. The lightweight cryptographic algorithms are classified into three types that are a public key, secret key, and hash functions. The symmetric and asymmetric cryptographic techniques are the two methods used for CoAP protocol security.
   A widely used cryptography technique to provide end-to-end security in CoAP is a symmetric technique, especially Advanced Encryption Standard (AES). The AES with 128-byte key size is a basic cipher suite of DTLS, and it avoids packet fragmentation and loss, and delay in the IoT environment. However, it generates different words using the original key, but it deduces the security level of CoAP by increasing the possibility of deriving the relationship between those words. Most of the available symmetric and asymmetric encryption schemes increase the burden on resource-restricted devices. Thus, the proposed work plans to optimize IoT security using lightweight and strong cryptography techniques.