With the widespread use and high-speed development of information technology and equipments,both individual and society depend more and more on network and electronic equipments,such as computers,mobile phone,etc.The following problem of information security is increasingly obviously.Encryption algorithm is an important method of protecting information security.However,with the development of quantum computer,many current conventional computer security encryption algorithms become unsafe,which also bring new challenges for the design of cryptosystem.Unconditional security is the highest-level secure cryptosystem which is unbreakable even when an attacker has unlimited time and unlimited resources.Perfect secrecy is unconditional security under the ciphertext-only attack.An attacker with unlimited time and unlimited computing power can’t get any information about the plaintext from the ciphertext.In 1949,one-time pad has been proved theoretically to be perfect secrecy by Shannon,but until now it is still not widely used.The main reasons include: 1)it is difficult to conveniently obtain a true random sequence as a key;2)one-time pad requires the key to be at least as long as the plaintext;3)there are difficulties in distribution and storage of keys of the length as required in the reason 2).To solve the practical problem of one-time pad,this paper proposed a dynamic cryptography system based on discrete trajectory transformation in generalized information domain(DCDG),the goal of which is to realize a practical and approximate one-time pad unconditional security cryptography system.The main contributions of this paper include:1.To solve the difficulty of obtaining a true random key in one-time pad,this paper proposed a random number generator based on generalized information domain and drift factor(RGDG-DF),which improved a Random number Generator based on Discrete trajectory transform in Generalized information domain(RGDG)proposed by the author’s group before.The new method accelerates RGDG and enhances the security.RGDG-DF uses generalized information domain which is randomly selected by the users as a true random source of entropy.Through reconstruction and discrete trajectory transformation based on the drift mechanism,the method can generate a random sequence of true random characteristics.Multiple randomness tests show that RGDG-DF has very good random properties.2.For the requirement of one-time key in one-time pad,RGDG–DF introduced the system initial value IV = {ST,SI,UI},which is not repeated in time and space.Among them,ST is the system time of each encryption,which is not repeated in the DCDG system lifetime;SI is a physical identifier with unique attributes,such as hard disk number,mainboard code,etc.;UI is user-defined.For any two times of encryption,because encryption time and encryption space(encryption machine)under practical conditions are mutually exclusive,IV has the uniqueness and randomness of time and space and with the user’s personalized information.The random sequence generated by RGDG-DF is decided by IV,the logic parameter and the reconstructed sequence,where IV and the logic parameter are parameters of the start position of the transformation.This paper proved that the random sequence generated by RGDG-DF system is not repeated in practical environment.3.In order to solve the difficulties of key distribution and storage in one-time pad where the length of key is the same as that of the plaintext,this paper uses the random selection of users on the generalized information domain and parameter setting as explicit key.Key = {GIF,S/L,D} is the secret of the sender and receiver,decided by communication parties.In this case,the user randomly specifies the generalized information file(GIF)as equivalent to specifying the true random information entropy source,and randomly select the reconstruction parameter S/L and the logic reconstruction parameter D.The properties of our system ensure that the same Key and different IV can generate non-duplicate keystreams.Analysis found that because the choice space of GIF is very large,the attacker can not break the Key through the exhaustive attack.Even if IV is known,the attacker can’t get the keystream without knowing the Key.Therefore,communication parties can use the Key for a long time after their appointment.In the encryption process,only IV needs to be transmitted along with the ciphertext,without the need to pass Key.4.This paper proposed a dynamic encryption algorithm framework,that is algorithms with fixed framework and changeable encryption details.Two new dynamic encryption algorithms have been proposed and applied to image encryption.Both of which have excellent encryption performance through experiment and theoretical analysis.5.The framework of DCDG encryption architecture is presented based on RGDG-DF and the dynamic encryption algorithm.The practicability and security of the frame are analyzed.Analysis results show that the DCDG approximately realizes one-time pad and can effectively resist ciphertext-only attack and other attacks.Thus,DCDG is practical unconditional security. |