Research Of The Fractional Hilbert Encryption Based On The Multirate

Along with the development of communication technology, the demand for data security is increasingly high.According to encryption key,encrpytion tachniques can be divided into two kinds : symmetric key cryptography and asymmetric encryption.The former have the same encryption key and decryption key,which have extensive used owing to its fast speed and simple implement.Making sure the security of encryption key is the system's sticking point.The Fractional Fourier Transform is the generalized format of the Fourier Transform.The latter is a linear operator whose rotation angle isπ/ 2 circumgyrate the time domain to frequency domain,while the Fractional Fourier Transform is a linear operator whose rotation angle is arbitrary circumgyrate the time domain to Fractional domain.Making the Fourier Transformation widening to Fractional Fourier Transform,also restrain the negative spectrum to fractional domain can get Fractional Hilbert Transform. The analytic signal based on the Fractional Hilbert Transform only contain the ortho-spectrum which can be gotten from the restrainability of the negative spectrum.Furthermore,this system can achieve security communication from making use of fractional angle of rotation.The filter bank based on the multirate theory widely used in audio signal and video signal processing , coding and identify . It can divide the signal into subband.According to the information of subband,the system can go along different processing.It can switch to polyphase structures via dividing transfer function into different phase.Also,this system can be efficient computing in virtue of equivalent transform,in which the convolution compute is converse to the low sample rate. The Fractional Hilbert encryption based on the multirate is belong to symmetric key cryptography.But this algorithms has only one secret key result in small keyspace.So this system must update the secret key regularity for security.In order to increase the keyspace,making use of filter bank in the communication system based on the Fractional Hilbert,the secret key can be turn into multiplex lead to large keyspace for security system.This paper introduce the current level of encryption and theory of Fractional Fourier Transform;Also,it analysis the principle Fractional Hilbert encryption and the filter bank's polyphase structures based on multirate theory.These lay the foundation for bringing forward a efficient method of multichannel encryption , which computation complexity is corresponding to one key encryption.The simulation experiment validate the valid and feasibility of this method.