Key aggregate cryptosystem for scalable data sharing in cloud storage
- 1. Key-Aggregate Cryptosystem for Scalable Data Sharing in Cloud Storage
- 2. INTRODUCTION Cloud computing provides the flexible architecture to share the application(software) as well as the other network resources(hardware) Cloud storage enables networked online storage where data is stored on multiple virtual servers, generally hosted by third parties , rather than being hosted on dedicated servers Key management and key sharing plays the main role in the data sharing concept of cloud computing
- 3. Traditional key cryptosystems lack the enhanced security techniques as the keys are generated by the existing random key generation Proposed system said to have aggregate key cryptosystem in which key generated by means of various derivations of cipher text class properties of data and its associated keys
- 4. DISADVANTAGES OF EXISTING SYSTEM Unexpected privilege escalation will expose all It is not efficient Shared data will not be secure The costs and complexities involved generally increase with the number of the decryption keys to be shared The encryption key and decryption key are different in public key encryption
- 5. ADVANTAGES OF PROPOSED SYSTEM It is more secure Decryption key is sent via a secure channel and kept secret It is an efficient public-key encryption scheme which supports flexible delegation The extracted key have can be an aggregate key which is as compact as a secret key for a single class The delegation of decryption can be efficiently implemented with the aggregate key
- 6. KEY-AGGREGATE ENCRYPTION A key aggregate encryption has five polynomial-time algorithms Setup Phase KeyGen Phase Encrypt Phase Extract Phase Decrypt Phase
- 7. SETUP PHASE The data owner executes the setup phase for an account on server which is not trusted The setup algorithm only takes implicit security parameter
- 8. KeyGen Phase This phase is executed by data owner to generate the public or the master key pair (pk, msk)
- 9. Encrypt Phase This phase is executed by anyone who wants to send the encrypted data Encrypt (pk, m, i), the encryption algorithm takes input as public parameters pk, a message m, and i denoting ciphertext class The algorithm encrypts message m and produces a ciphertext C such that only a user that has a set of attributes that satisfies the access structure is able to decrypt the message Input= public key pk, an index i, and message m Output = ciphertext C
- 10. Extract Phase This is executed by the data owner for delegating the decrypting power for a certain set of ciphertext classes to a delegate Input = master-secret key mk and a set S of indices corresponding to different classes Outputs = aggregate key for set S denoted by kS
- 11. Decrypt Phase This is executed by the candidate who has the decryption authorities. Decrypt (kS, S, i, C), the decryption algorithm takes input as public parameters pk, a ciphertext C, i denoting ciphertext classes for a set S of attributes Input = kS and the set S, where index i = ciphertext class Outputs = m if i element of S
- 12. Conclusion To share data flexibly is vital thing in cloud computing Users prefer to upload there data on cloud and among different users Outsourcing of data to server may lead to leak the private data of user to everyone Encryption is a one solution which provides to share selected data with desired candidate Sharing of decryption keys in secure way plays important role Public-key cryptosystems provides delegation of secret keys for different ciphertext classes in cloud storage The delegatee gets securely an aggregate key of constant size It is required to keep enough number of cipher texts classes as they increase fast and the ciphertext classes are bounded that is the limitation