A New Cryptography Scheme Based on Laplace Transform and a Substitution-Permutation Network

The aim of cryptography is to convert plaintext into ciphertext which can be transmitted via insecure communication channels, so that, it impossible this ciphertext cannot be used for plaintext reproduction without knowing the corresponding key. Certain current Laplace transformation-based encryption methods have been proven to exhibit various security defects, such as the size of the secret key used for decryption usually greater than the size of the Plaintext, because that the secret key represents the quotient of Laplace transform values on 26, and these values larger than plaintext values. Therefore ,the encryption process is not important, as well as the possibility of obtaining the plaintext without knowing the secret key. To solve this problem, this paper proposes a new scheme cryptosystem based on Laplace Transform with using substitution boxes. The message is encrypted in many cycles, the secret key is added in each cycle and resultants values from the Laplace transform are substituting with the corresponding values from the substitution box that would be determined based on quotient and remainder values of Laplace transform values on block length. The security analysis and statistical results demonstrate that the proposed scheme provides a higher security level against different cryptographic attacks.