COST-EFFECTIVE AUTHENTIC AND ANONYMOUS

DATA SHARING WITH FORWARD SECURITY

CONTENT

Introduction

Problem statements

Literature Review

Existing system

Proposed system

Application

Conclusion

Future work

MOTIVATIONS

Cloud Computing is ceaseless growing latest technology in IT industry,

academia and business. Main features of cloud computing is that on-demand

capabilities, broad network access, resource pooling, rapid elasticity ,measured

service scalability and provides shared services to user on demand basis in

distributed environment.

Data sharing :One of the government officials wants to leak a secret to the

public, however he wants to remain anonymous. On the other hand, he wants

the public to be convinced that the secret is actually leaked from one of the

many officers and is thus reliable.

So, we want a signature scheme to have the properties of correctness,

unforgeabilitiy, and anonymous.

INTRODUCTION

The popularity and widespread use of “CLOUD” have brought great

convenience for data sharing and collaboration .

Example: Smart Grid

Taking energy usage data sharing in Smart Grid as an example, there are

several security goals a practical system must meet, including:

1. Data Authenticity.

2. Anonymity

3. Efficiency.

PROBLEM AND SOLUTION STATEMENTS

Problem :

Data sharing has never been easier with the advances of cloud computing as data is

always deployed in a hostile environment and vulnerable to a number of security threats.

Yet the costly certificate verification and validation in the traditional public key

infrastructure (PKI) setting becomes a bottleneck for data sharing solution to be scalable

Solution :

Ring signature is a promising candidate to construct an anonymous and authentic data

sharing system. It allows a data owner to anonymously authenticate his data which can be

put into the cloud for storage or analysis purpose.

Identity-based (ID-based) ring signature, which eliminates the process of certificate

verification, can be used instead of traditional public key infrastructure (PKI).

LITERATURE REVIEW

Hui Wang. Privacy-preserving Data Sharing In Cloud Computing. Journal Of

Computer Science AndTechnology 25(3): 401–414 May 2010.

Considered two kinds of privacy leakage, presence leakage, which is to identify an

individual in (or not in) the dataset, and association leakage, which is to identify

whether an individual is associated with some sensitive information, e.g., a specific

disease. Author defined α- presence and β-association to address these two kinds of

privacy leakage in a unified framework. Author developed a novel technique,

Ambiguity, that protects both presence privacy and association privacy.

CONT…

Sherman S.M. Chow, S.M. Yiu, and Lucas C.K. Hui Department of Computer

Science The University of Hong Kong Pokfulam, Hong Kong “Efficient

Identity Based Ring Signature ” International Association for Cryptologic

Research 2014

For ring signature schemes to be practical, system need to eliminate the need for

validity checking of the certificates and the need for registering for a certificate

before getting the public key. ID-based solutions can provide these two features.

CONT…

Forward-Secure Digital Signature Scheme MihirBellare and Sara K. Miner ”A Forward-

Secure Digital Signature Scheme” Dept. of Computer Science, & Engineering University

of California at San Diego, 9500 Gilman Drive La Jolla, CA 92093, USA

Digital signature scheme in which the public key is fine-tuned but the secret signing

key is updated at customary intervals so as to provide forward security property:

compromise of the current secret key does not enable an adversary to forge

signatures pertaining to the past. This can be utilizable to mitigate the damage

caused by key exposure without requiring distribution of keys.

“ Past signature remain secure even if expose the current secret key.”

EXISTING SYSTEM

Identity-based Cryptography

In 1984, Adi Shamir, of RSA notoriety, introduced the concept of identity-based

cryptography. which eliminated the need for verifying the validity of public key

certificates, the management of which is both time and cost consuming.

In an ID-based cryptosystem, the public key of each user is publicly known identity

(e.g., an email address, a residential address, etc.). And then private key generator

(PKG) then computes private keys from its master secret for users.

Problem Inherent key escrow : Escrow systems are somewhat risky because a third

party is involved in marinating and issuing of private key

CONT…

Ring Signatures

Ring signatures were invented by Ron Rivest, Adi Shamir, and Yael Tauman. Ring

Signature is type of digital signature that can be performed by any member of a

group having key . Therefore, a message signed with a ring signature, is signed by

someone in a particular group of people. However it is computationally infeasible to

determine which of the group members' keys was used to produce the signature.

ID-BASED RING SIGNATURE

ALGORITHM

ID-based ring signature is more preferable in the setting with a large number of users such as

energy data sharing in smart grid:

Step 1: The energy data owner (say, Bob) first setups a ring by choosing a group of users.

This phase only needs the public identity information of ring members, such as residential

addresses, and Bob does not need the collaboration (or the consent) from any ring

members.

Step 2: Bob uploads his personal data of electronic usage, together with a ring signature

and the identity information of all ring members.

Step 3: By verifying the ring signature, one can be assured that the data is indeed given out

by a valid resident (from the ring members) while cannot figure out who the resident is.

Hence the anonymity of the data provider is ensured together with data authenticity.

KEY EXPOSURE PROBLEM

Problem :Key Exposure Problem in Id-based Ring signature:

If the private key of a signer is compromised , all signatures of that signer

become worthless: future signatures are invalidated and no previously issued

signatures can be trusted.

Solution : ID-based Forward Secure Ring Signature

The notion of forward secure signature was proposed to preserve the validity of

past signatures even if the current secret key is compromised.

The idea is dividing the total time of the validity of a public key into T time

periods, and a key compromise of the current time slot does not enable an

adversary to produce valid signatures pertaining to past time slots.

PROPOSED SYSTEM :ID-BASED FORWARD

SECURE RING SIGNATURE (IDFSRS)

ID-based forward secure ring signature scheme are designed in following ways. The

identities and user secret keys are valid into T periods and makes the time intervals

public and also set the message space M= { 0,1 }.

It is in ID-based setting.

The size of a secret key is just one integer.

Key update process only requires an exponentiation.

IDFSRS do not require any pairing in any stage.

ALGORITHM

A (1,n) ID-based forward secure ring signature (IDFSRS) scheme is a tuple of probabilistic polynomial-time

(PPT) algorithms:

Setup. On input an unary string 1λ where λ is a security parameter, the algorithm outputs a master secret

key msk for the third party private key generator and a list of system parameters param that includes λ and

the description of a user secret key space D, a message space M as well as a signature space ψ.

Extract. On input a list param of system parameters, an identity IDi ϵ {0,1}* for a user and master secret

key ski,0 ϵ D such that the secret key is valid for time t=0. In this algorithm we denote IDi corresponds to

user secret key ski,0 or vice versa, we mean the pair (IDi , ski,0) is an input-output pair of Extract with

respect to param and mask.

o Update. On input a user secret key ski,t for a time period t, the algorithm outputs a new user secret key

ski,t+1 for the time period t+1.

Sign. On input a list param of system parameters, a time period t, a group size n of length polynomial in λ, a set L={IDi ϵ {0,1}*|i ϵ [1,n]} of n user identities, a message m ϵ M, and a secret key skπ,t ϵ D, π ϵ [1,n] for

time period t, the algorithm outputs a signature σ ϵ ψ.

Verify. On input a list param of system parameters, a time period t, a group size n of length polynomial in

λ, a set L={IDi ϵ {0,1}*|i ϵ [1,n]} of n user identities, a message m ϵ M, a signature σ ϵ ψ , it output either

valid or invalid.

APPLICATIONS OF FORWARD SECURE ID-BASED

RING SIGNATURES

WHISTLE BLOWING

ONLINE BANKING

MAIL BOX.

CONCLUSION

IDFSRS allows an ID-based ring signature scheme to have forward security

and can be proven forward-secure unforgeable in the random oracle model ,

assuming RSA problem is hard.

IDFSRS is very efficient and does not require any pairing operations. The size

of user secret key is just one integer, while the key update process only

requires an exponentiation.

IDFSRS scheme will be very useful in many other practical applications,

especially to those require user privacy and authentication, such as ad-hoc

network, e-commerce activities and smart grid.

FUTURE WORK

Our current scheme relies on the random oracle assumption to prove its

security. We consider a provably secure scheme with the same features in the

standard model as an open problem and our future research work.

REFERENCES

[1]. Abe, M. Ohkubo, and K. Suzuki, “1-out-of-n signatures from a variety of keys,” in Proc.

8th Int. Conf. Theory Appl. Cryptol. Inform. Security: Adv. Cryptol., 2002, vol. 2501, pp. 415–

432.

[2] R. Anderson, “Two remarks on public-key cryptology,” Manuscript,Sep. 2000. (Relevant

material presented by the author in an invited lecture at the Fourth ACM Conference on

Computer and Communications Security, 1997.)

[3] G. Ateniese, J. Camenisch, M. Joye, and G. Tsudik, “A practical and provably secure

coalition-resistant group signature scheme,” in Proc. 20th Annu. Int. Cryptol. Conf. Adv.

Cryptol., 2000, vol. 1880, pp. 255–270.

[4] M. H. Au, J. K. Liu, T. H. Yuen, and D. S. Wong, “ID-based ring signature scheme secure in

the standard model,” in Proc. 1st Int.Workshop Security Adv. Inform. Comput. Security,

2006, vol. 4266,pp. 1–16.

[5] A. K. Awasthi and S. Lal, “Id-based ring signature and proxy ring signature schemes from

bilinear pairings,” CoRR, vol. abs/cs/0504097, 2005.

Thank you