This document presents a proposed system for secure and flexible data sharing in cloud storage. It describes using new public-key cryptosystems that can aggregate any set of secret keys into a constant-size ciphertext. This allows flexible sharing of encrypted data through an aggregate key that decrypts multiple ciphertexts without increasing in size. The system architecture includes setup, encryption, key generation, and decryption phases. The proposed system aims to address limitations in existing approaches regarding key sizes and flexibility of data access delegation.

1. T.SRAVANI
(11541A0538)
G.KOTESWARA RAO M.ABHILASH
(11541A0509) (11541A0521)
P.SHEETALCHAITANYA M.VASUDEVA REDDY
(11541A0529) (11541A0515)
Under The Guidence Of
G.SURESH KUMAR, M.Tech

2. CONTENTS
 Introduction
 Abstract
 Existing System
 Proposed System
 System Architecture
 Modules
 System Requirements

3. INTRODUCTION
 The word Cloud Computing mean?
 What does Cloud Computing mean?
 In the Cloud Computing the apps and files are hosted
consisting of thousands of computers and servers &and
linked together ,they are accessed via internet.
 By using Cloud Computing we can access all the apps and
documents from anywhere in the world.

4. ABSTRACT
 Data sharing is an important functionality in cloud storage.
 Here we show how to securely, efficiently, and flexibly
share data with others in cloud storage.
 We describe new public-key cryptosystems that produce
constant-size ciphertexts.
 One can aggregate any set of secret keys and make them as
compact as a single key, but encompassing the power of all
the keys being aggregated.

5.  The secret key holder can release a constant-size
aggregate key for flexible choices of ciphertext set.
 This compact aggregate key can be conveniently sent
to others or be stored in a smart card with very
limited secure storage.
 We also describe other application of our schemes.
 In particular, our schemes give the first public-key
patient-controlled encryption for flexible hierarchy,
which was yet to be known.

6. EXISTING SYSTEM
 Considering data privacy, a traditional way to ensure
it is to access control after authentication, which
means any unexpected privilege escalation will
expose all data.
 In a shared-tenancy cloud computing environment,
things become even worse.
 Regarding availability of files, there are a series of
cryptographic schemes which go as far as allowing a
third-party auditor to check the availability of files of
the data owner without leaking

7. DISADVANTAGES OF EXISTING SYSTEM
 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 publickey encryption.

8. PROPOSED SYSTEM
 In this paper, we study how to make a decryption key
more powerful in the sense that it allows decryption
of multiple ciphertexts, without increasing its size.
 Specifically, our problem statement is “To design an
efficient public-key encryption scheme which
supports flexible delegation in the sense that
any subset of the ciphertexts is decry ptable by a
constant-size decryption key ”.
 We solve this problem by introducing a special type
of public-key encryption which we call key-aggregate
cryptosystem (KAC).

9.  In KAC, users encrypt a message not only under a
public-key, but also under an identifier of
ciphertext called class.
 The key owner holds a master-secret called
master-secret key, which can be used to extract
secret keys for different classes.
 the extracted key have can be an aggregate key
which is as compact as a secret key for a single
class, but aggregates the power of many such
keys

10. ADVANTAGES OF PROPOSED SYSTEM
 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.

11. SYSTEM ARCHITECTURE

12. MODULES
 Setup Phase
 Encrypt Phase
 Key Gen Phase
 Decrypt Phase

13. Setup Phase
 The setup algorithm takes no input other than the
implicit security parameter.
 It outputs the public parameters PK and a master key
MK.

14. Encrypt Phase
 Encrypt(PK,M, A). The encryption algorithm takes as
input the public parameters PK, a message M, and an
access structure A over the universe of attributes.
 The algorithm will encrypt M and produce a ciphertext
CT such that only a user that possesses a set of
attributes that satisfies the structure will be able to
decrypt the message.

15. Key Gen Phase
 Key Generation(MK,S). The key generation algorithm takes
as input the master key MK and a set of attributes S that
describe the key. It outputs a private key SK .
 This can be observed in the architecture as shown in the
next slide

17. Decrypt Phase
 Decrypt(PK, CT, SK). The decryption algorithm takes
as input the public parameters PK, a ciphertext CT,
which contains an access policy A, and a privatekey SK,
which is a private key for a set S of attributes.
 If the set S of attributes satisfies the access structure A
then the algorithm will decrypt the ciphertext and
return a message M.

18. SYSTEM REQUIREMENTS
HARDWARE REQUIREMENTS:-
 System : Intel i3 processor
 Hard Disk : 40 GB
 Monitor : 15 VGA Colour
 Ram : 1 Gb
SOFTWARE REQUIREMENTS:-
 Operating system : Windows XP/7.
 Coding Language : JAVA/J2EE
 IDE : Netbeans 7.4
 Database : MYSQL