Knapsack Encryption algorithm is a public key encryption technique whose strength depends solely on the super increasing sequence used as the private key. Our target is to find out the plain text from the available cipher text and public key. Nature inspired algorithms (NIA) have been of great help in searching problems. Since the searching of plain text is of exponential order, nature inspired algorithms can help searching the space smartly. In recent times, many new algorithms have been proposed which are inspired from nature and its creations. One such algorithm is Dingo Optimizer, which we have used here for cryptanalysis of Knapsack Cryptosystem. A new fitness function is introduced here and the results obtained in our work are quite favorable. The experimental findings convey that Dingo based cryptanalysis outperforms the earlier reported approaches.