ABSTRACT
One of the first methods to show promise for a replacement for Advanced Encryption Standard (AES) for light-weight cryptography was PRESENT. It uses smaller block sizes and has the potential for smaller keys. PRESENT uses either an 80-bit or a 128-bit encryption key. It operates on 64 bit block and uses a substitution-permutation network (SPN) method. With SPN, as with AES, we operate on blocks of plaintext and apply a key and then use a number of rounds which we use substitution boxes and permutation boxes. The main contenders for quantum robust methods are: Lattice-based cryptography; Code-based cryptography; Multivariate polynomial cryptography; and Hash-based signatures. A Merkle tree defines each non-leaf node with a value or a label and contains a hash of its children. This builds a hash trees and is used to provide a verification of large-scale data structures.
