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Data deduplication is one of important data compression techniques for eliminating duplicate copies of repeating data, and has been widely used in cloud storage to reduce the amount of storage space and save bandwidth. To protect the confidentiality of sensitive data while supporting deduplication, the convergent encryption technique has been proposed to encrypt the data before outsourcing. To better protect data security, this paper makes the first attempt to formally address the problem of authorized data deduplication. Different from traditional deduplication systems, the differential privileges of users are further considered in duplicate check besides the data itself.We also present several new deduplication constructions supporting authorized duplicate check in a hybrid cloud architecture. Security analysis demonstrates that our scheme is secure in terms of the definitions specified in the proposed security model. As a proof of concept, we implement a prototype of our proposed authorized duplicate check scheme and conduct testbed experiments using our prototype. We show that our proposed authorized duplicate check scheme incurs minimal overhead compared to normal operations.


To make data management scalable in cloud computing, deduplication has been a well-known technique and has attracted more and more attention recently. Data deduplication is a specialized data compression technique for eliminating duplicate copies of repeating data in storage. The technique is used to improve storage utilization and can also be applied to network data transfers to reduce the number of bytes that must be sent. Instead of keeping multiple data copies with the same content, deduplication eliminates redundant data by keeping only one physical copy and referring other redundant data to that copy. Deduplication can take place at either the file level or the block level. For filelevel deduplication, it eliminates duplicate copies of the same file. Deduplication can also take place at the block level, which eliminates duplicate blocks of data that occur in non-identical files.


  • Users’ sensitive data are susceptible to both insider and outsider attacks.
  • Some times deduplication impossible.


Convergent encryption has been proposed to enforce data confidentiality while making deduplication feasible. It encrypts/decrypts a data copy with a convergent key, which is obtained by computing the cryptographic hash value of the content of the data copy. After key generation and data encryption, users retain the keys and send the ciphertext to the cloud. Since the encryption operation is deterministic and is derived from the data content, identical data copies will generate

same convergent key and hence the same ciphertext. To prevent unauthorized access, a secure proof of ownership protocol is also needed to provide the proof that the user indeed owns the same file when a duplicate is found. After the proof, subsequent users with the same file will be provided a pointer from the server without needing to upload the same file. A user can download the encrypted file with the pointer from the server, which can only be decrypted by the corresponding data owners with their convergent keys. Thus, convergent encryption allows the cloud to perform deduplication on the ciphertexts and the proof of ownership prevents the unauthorized user to access the file. However, previous deduplication systems cannot support differential authorization duplicate check, which is important in many applications. In such an authorized deduplication system, each user is issued a set of privileges during system initialization each file uploaded to cloud is also bounded by a set of privileges to specify which kind of users is allowed to perform the duplicate check and access the files.


  • It makes overhead to minimal compared to the normal convergent encryption and file upload operations.
  • Data confidentiality is maintained.
  • Secure compared to existing techniques.


hybrid cloud


üProcessor                  -        Pentium –IV

üSpeed                        -        1.1 Ghz

üRAM                         -        512 MB(min)

üHard Disk                 -        40 GB

üKey Board                -        Standard Windows Keyboard

üMouse                       -        Two or Three Button Mouse

üMonitor                     -        LCD/LED


  • Operating system:         Windows XP
  • Coding Language:         Java
  • Data Base             :         MySQL
  • Tool                     :         Net Beans IDE


Jin Li, Yan Kit Li, Xiaofeng Chen, Patrick P. C. Lee, Wenjing Lou“A Hybrid Cloud Approach for Secure Authorized Deduplication” IEEE TRANSACTIONS ON PARALLEL AND DISTRIBUTED SYSTEMS, Volume:PP ,  Issue: 99 , April 2014.

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