A New Cryptosystem Based on Three Knapsacks with Plaintext Encoding

In this paper, we propose a transformed knapsack cryptosystem by using three knapsacks with plaintext encoding to enhance the security of Knapsack cryptosystem. In our approach we try to encode a plaintext before encrypting. The benefits are that using plaintext encoding method can not only increase the density of the knapsack, but also reduce decrypt time substantially. The ciphertext is composed by multiplying two non-superincreasing knapsacks and then add to a superincreasing knapsack. Our propose scheme can be secure against the low density attack because the plaintext encoding the density can be made as large as our desire.