The document discusses a proposed system called functional encryption with payable outsourced decryption (FEPOD) that uses blockchain technology. FEPOD allows outsourcing decryption tasks to an untrusted third party while enabling payment through cryptocurrency processed on the blockchain. It defines the security model for FEPOD and presents a generic construction along with analyzing its security. The system was implemented on a blockchain platform to evaluate feasibility. FEPOD allows verification of outsourced decryption results and zero-knowledge contingent payments between users and third parties performing the decryption tasks.

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Pay as You Decrypt Decryption Outsourcing for Functional
Encryption Using Blockchain
Abstract
The concept of functional encryption (FE) has been introduced to address the shortcomings of
public-key encryption (PKE) in many emerging applications which require both data storage and
data sharing (e.g., cloud storage service). One of the major issues existing in most FE schemes is
the efficiency, as they are built from bilinear pairings of which the computation is very
expensive. A widely accepted solution to this problem is outsourcing the heavy workloads to a
powerful third party and leaving the user with the light computation. Nevertheless, it is
impractical to assume that the third party (e.g., the cloud) will provide free services. To our
knowledge, no attention has been paid to the payment procedure between the user and the third
party in an FE with outsourced decryption (FEOD) scheme under the assumption that neither of
them should be trusted. Leveraging the transactions on cryptocurrencies supported by the
blockchain technology, in this paper, we aim to design FE with payable outsourced decryption
(FEPOD) schemes. The payment in an FEPOD scheme is achieved through a blockchain-based
cryptocurrency, which enables the user to pay a third party when it correctly completes the
outsourced decryption. We define the adversarial model for FEPOD schemes, and then present a
generic construction of FEPOD schemes. Also, we evaluate the performance of the proposed
generic construction by implementing a concrete FEPOD scheme over a blockchain platform.
Index Terms—Cloud storage, blockchain, outsourced decryption.
Existing System:
Intuitively, these two problems can be simply solved by introducing a trusted authority (e.g., the
bank) to serve as an intermediary. This method, however, makes all transactions transparent to
the authority, which is unsatisfactory for the user who expects his/her personal privacy to be
protected. The emerging blockchain technology provides a decentralized and self-enforceable
solution for the fair payment between Alice and Bob. Blockchain-based platforms (e.g.,
Ethereum [8]) are capable of executing a smart contract between Alice and Bob. Alice can post a
payable outsourcing computation smart contract to the blockchain, which describes the
outsourcing computation task as well as the rules for settling the payment. The smart contract
states that whoever provides the correct solution can claim a pre-determined reward. In essence,
the blockchain here is serving as the traditional role of a trusted third party. Alice “deposits”
funds in the blockchain, and the blockchain will release those funds to Bob if and only if Bob is
able to provide the accurate answer. In order to participate the computation tasks, Bob also needs
to “deposits” funds in the blockchain, and he will be penalized for any malicious behaviour.

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we focus on designing functional encryption with payable outsourced decryption (FEPOD)
schemes in a generic way (i.e., the given generic construction should be applicable to most of the
FEOD schemes), where the payment can be accomplished via a blockchain-based
cryptocurrency. An FEPOD scheme should enable efficient and public verification for the
outcome of the outsourced decryption task. In other words, in an FEPOD scheme, anybody
should be able to efficiently verify the correctness of the result solely based on the given public
information.
Proposed System:
We propose a notion of functional encryption with payable outsourced decryption (FEPOD),
which allows anybody to check the correctness of the answer for the outsourcing computation
task provided by an untrusted third party such that the payment can be processed by a
blockchain-based cryptocurrency.
• We delineate the security model of an FEPOD scheme, present a generic construction of it, and
analyse its security.
• We implement a concrete FEPOD scheme, which is derived from the generic construction,
over a blockchain platform to evaluate its feasibility and practicality.
Advantages:
Outsourcing Computation.
Zero-Knowledge Contingent Payments.
System Architecture:

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SYSTEM REQUIREMENTS:
HARDWARE REQUIREMENTS:
• PROCESSOR : I3.
• Hard Disk : 40 GB.
• Ram : 2 GB.
SOFTWARE REQUIREMENTS:
• Operating system : Windows.
• Coding Language : JAVA/J2EE
• Data Base : MYSQL
• IDE :Netbeans8.1