Research On Group Public Key Cryptosystem With Equality Test

Public key encryption with equality test(PKEET)is an emerging searchable encryption technology that aims to provide privacy protection for data in open network channels while enhancing the availability of encrypted data.This cryptographic primitive allows authorized third parties to perform equality test algorithms for ciphertexts without executing decryption operations,comparing whether the contents of two ciphertexts encrypted under different public keys are the same.However,existing group public key encryption with equality test schemes can only support one-to-one data sharing,which will cause huge computational and storage burdens when implementing one-to-many data sharing.In addition,most PKEET schemes only support the exact comparison of ciphertext contents.If there is a syntax error in the user’s input query,then the user will not get the expected retrieval results.The objective of this thesis is to offer solutions to the aforementioned issues,and conducts in-depth research on the cryptosystem and applications of PKEET,achieving the following results:(1)This thesis proposes a group attribute-based encryption with equality test scheme.The scheme allows users to encrypt intended shared data using an access policy and embed attribute information into the secret keys of users.Only users’ secret keys that satisfy the policy can decrypt the data,enabling differentiated access control for multiple users.Additionally,the scheme employs a group-granularity authorization mechanism where the authorized third party could only perform equality tests on user ciphertexts from the same group.If the two ciphertexts belong to users in different groups,they cannot be subjected to the ciphertext equivalence test.The scheme forbids the third party to hold the group user’s public keys for encryption,thereby making it resistant to attacks where the third-party attempts to recover the message by guessing from a given ciphertext through exhaustive search.The scheme’s efficiency,security,and practicality are demonstrated through theoretical analysis and experimental verification.(2)This thesis proposes a public key encryption scheme with equality test that supports efficient fuzzy matching.The scheme uses locality-sensitive hashing and Bloom filters to generate a corresponding bit vector representation for plaintext messages.The similarity between message contents is measured by the Euclidean distance between the corresponding message vectors.In the locality-sensitive hash function,two vectors with a distance smaller than a given threshold have a high probability of having the same hash result.The scheme utilizes this feature to compare the hash values of encrypted message vectors and thus achieves fuzzy matching of ciphertext contents.The proposed scheme does not require preprocessing of the character set and enjoys constant computational costs in the encryption,decryption,and fuzzy matching stages.The computational complexity is not affected by the length of the message and this scheme could handle various syntax errors.The security of this scheme is rigorously analyzed,and experimental results show that it has high efficiency in fuzzy queries and can be applied in various cloud computing scenarios.