How to Hide the Real Receiver Under the Cover Receiver: CP-ABE With Policy Deniability

Po-Wen Chi,Ming-Hung Wang,Hung-Jr Shiu

doi:10.1109/access.2020.2993688

Abstract

Attribute-based encryption (ABE) is a useful tool for sharing an encrypted data to a target group. In a ciphertext-policy ABE (CP-ABE) scheme, a ciphertext includes a policy to indicate its receivers and only those receivers can correctly decrypt the ciphertext. Since this design leaks the receiver identity, it may raise a new security issue about user privacy. Some hidden-policy ABE schemes, where the policy is secretly protected, are proposed to keep user privacy. However, these hidden-policy ABE schemes rely on the user trying all possibilities to decide if it belongs to the wanted receiver group. The decryption costs too much and every potential receiver will run the decryption process in vain since it does not know the policy. In this work, we apply the deniability concept to solve this problem. The encryption scheme allows the sender to claim the ciphertext is for some receiver group while actually it is for another receiver group. Both receiver groups can correctly decrypt the ciphertext except that the real group can get the real message and the cover group will get the cover message. While coercion, the sender can definitely claim the ciphertext is for the cover group and the real group is kept confidential.

Highlights

Encryption techniques are useful tools to protect data confidentiality
WORK In this paper, we propose a CDP-Attribute-based encryption (ABE) scheme
Compared to other ciphertext-policy attribute-based encryption (CP-ABE) schemes, ciphertext-deniable-policy ABE scheme (CDP-ABE) scheme makes a ciphertext include more than one access policy, one is the real policy and the other is the cover policy

Summary

INTRODUCTION

Encryption techniques are useful tools to protect data confidentiality. Generally speaking, a sender and a receiver need to share information before they can communicate securely. This technique is often applied to digital right management services because copyright owners want to embed their signatures into their works without being noticed Following this concept, in this paper, we ask a similar question, is it possible to hide the real receiver identity under another cover receiver identity in one ciphertext? The ‘‘successful decryption’’ means that both Bob and Charles can get meaningful messages, which are prepared by the sender, after their decryption operations When questioned by her mother, Alice can claim the ciphertext is for Bob and reveals the message sent to Bob. Bob can be an honest witness because he only knows what he received.

DENIABLE ENCRYPTION

PRELIMINARIES

CONSTRUCTION

DISCUSSION

CONCLUSION AND FUTURE WORK