Design And Implementation Of File Encryption System Based On Certificateless Multi-receiver Signcryption

Nowadays,many applications with file encryption function have appeared on the market.These software applications provide users with convenient and quick file encryption operations while also ensuring the security of user data.Files can exist in the form of cipher text on local,cloud server and third-party applications.The file encryption schemes selected by existing applications are divided into two types: symmetric encryption and asymmetric encryption.Symmetric encryption means that the user uses the same key in the encryption and decryption process.This type of scheme has high encryption efficiency,and the form of expression is mostly "one-time-pad".A key is negotiated before each encryption,and the key will become invalid after the decryption is completed.But the disadvantage is that the sender and receiver need to negotiate a key face-to-face before encryption or complete key negotiation with the help of a key exchange protocol.Asymmetric encryption means that each user has two keys,a public key and a private key.The public key is published to everyone,while the private key is kept by the user and not published.In this type of scheme,the sender uses the receiver's public key to encrypt the plaintext,and the receiver uses its own private key to decrypt the ciphertext.The private key cannot be calculated from the public key.However,most of the asymmetric encryption schemes have complex public key certificate management or key escrow problems.Later,researchers proposed a certificateless encryption system to solve the above problems.With the application and popularization of encryption technology,the traditional one-to-one encryption method can no longer meet the needs of communication.Some fields are more suitable for one-to-many encryption methods,such as message group sending,broadcast multicast,video conference and so on.Therefore,how to design a signcryption scheme based on certificateless multiple acceptors is a problem that needs to be studied and solved urgently.In response to the above problems,the work of this thesis mainly starts from two aspects.On the one hand,design a multi-receiver signcryption scheme based on certificateless.This solution discards the bilinear pairing operation used in the previous solution,and uses elliptic curve algebra with lower computational complexity,which reduces the amount of calculation during encryption and decryption,and improves the efficiency of encryption and decryption.In order to realize the anonymity of the recipient,this scheme integrates the polynomial technology and the identity of the recipient to realize the anonymity of the recipient.In this scheme,the user's public and private keys are composed of two parts.One part is generated by the user,and the other part is generated by the key generation center(KGC for short)and sent to the user through a public channel.Compared with other schemes,it prevents KGC maliciously steals user keys and reduces communication overhead.On the other hand,this thesis uses the scheme as the core of the encryption and decryption module,and designs a file encryption system based on the C/S architecture.After logging in to the encryption system,users can obtain their own public and private key pairs,which can encrypt files and send them to recipients through public channels.The recipients can decrypt the files in the system to obtain plaintext,ensuring the security of the files.