The document summarizes a research paper that analyzes the security of a decentralized key-policy attribute-based encryption (ABE) scheme proposed by Han et al. The summary states that while Han et al. claimed their ABE scheme achieved better privacy for users and was provably secure, after careful reexamination the scheme was found to be vulnerable to collusion attacks and failed to meet basic security definitions for ABE systems. A new ABE system is proposed that can resist collusion attacks.

1. Security Analysis of a Privacy-Preserving Decentralized
Key-Policy Attribute-Based Encryption Scheme
ABSTRACT:
In a decentralized attribute-based encryption (ABE) system, any party can act as an
authority by creating a public key and issuing private keys to different users that
reflect their attributes without any collaboration. Such an ABE scheme can
eliminate the burden of heavy communication and collaborative computation in the
setup phase of multi-authority ABE schemes, thus is considered more preferable.
Recently in IEEE Trans. Parallel Distrib. Syst., Han et al. [3] proposed an
interesting privacy-preserving decentralized key-policy ABE scheme, which was
claimed to achieve better privacy for users and to be provably secure in the
standard model. However, after carefully revisiting the scheme, we conclude that
their scheme cannot resist the collusion attacks, hence fails to meet the basic
security definitions of the ABE system.
EXISTING SYSTEM:
As attribute-based encryption (ABE) can simultaneously provide flexible access
control and data confidentiality functionalities, it has become a promising

2. technique for building secure access in practical distributed systems. Very recently,
Han et al. proposed a decentralized key-policy ABE scheme in the standard model,
based on which, they proposed a privacy preserving key extraction protocol to
protect the user’s identifier. They also claimed that they solved the challenging
open problem left by Chase and Chow by constructing a privacy preserving multi-
authority ABE scheme without interactions among the authorities
DISADVANTAGES OF EXISTING SYSTEM:
However, after carefully analyzing the existing scheme, we found that this scheme
is vulnerable to the collusion attack, which is a basic security requirements for
ABEs systems.
PROPOSED SYSTEM:
Recently in IEEE Trans. Parallel Distrib. Syst., Han et al. [3] proposed an
interesting privacy-preserving decentralized key-policy ABE scheme, which was
claimed to achieve better privacy for users and to be provably secure in the
standard model. However, after carefully revisiting the scheme, we conclude that
their scheme cannot resist the collusion attacks, hence fails to meet the basic
security definitions of the ABE system.
We propose a new system that can resist collusion attacks.

3. ADVANTAGES OF PROPOSED SYSTEM:
Overcome the drawback of collusion attacks which is in existing system.
SYSTEM CONFIGURATION:-
HARDWARE CONFIGURATION:-
 Processor - Pentium –IV
 Speed - 1.1 Ghz
 RAM - 256 MB(min)
 Hard Disk - 20 GB
 Key Board - Standard Windows Keyboard
 Mouse - Two or Three Button Mouse
 Monitor - SVGA

4. SOFTWARE CONFIGURATION:-
 Operating System : Windows XP
 Programming Language : JAVA
 Java Version : JDK 1.6 & above.
REFERENCE:
Aijun Ge, Jiang Zhang, Rui Zhang, Chuangui Ma, and Zhenfeng Zhang, “Security
Analysis of a Privacy-Preserving Decentralized Key-Policy Attribute-Based
Encryption Scheme”, IEEE TRANSACTIONS ON PARALLEL AND
DISTRIBUTED SYSTEMS, 2013.