Homomorphic Hash and Blockchain Based
Authentication Key Exchange Protocol for Strangers
Hailong Yao
School of Electronic and
Information Engineering
Lanzhou City University
Lanzhou, Cina
Hailong.Yao@outlook.com
Caifen Wang
College of Computer Science &
Engineering
Northwest Normal University
Lanzhou, Cina
wangcf@nwnu.edu.cn
Bo Hai
School of Electronic and
Information Engineering
Lanzhou City University
Lanzhou, Cina
Haibo@lzcu.edu.cn
Shiqiang Zhu
School of Electronic and
Information Engineering
Lanzhou City University
Lanzhou, Cina
Zhusq@lzcu.edu.cn
Abstract—Modern communication technologies and
cryptographic technologies have pushed social networks into the
virtual world, but they have also ensured the real existence of
social proximity. In the evaluation of social proximity, some
decentralized scenarios require the participants bootstrapping
tust, and the existing authentication key exchange scheme can
hardly satisfy the above requirements. In this study, we have
designed a homomorphic hash and Blockchain based
authenticated key exchange protocol with privacy protection, and
prove its security under the standard model based on hash one-
way, discrete logarithm and Blockchain transaction-level security
assumption, and discussed the attack that the proposed scheme
can resist. Compared with the existing scheme, the proposed
scheme does not need the default Unit of Trust, is safer and more
flexible, suitable for the scenarios that require strangers to
bootstrap trust.
Keywords—Authenticated Key Exchange Protocol, Bootstrap
Trust, Privacy Protection, Homomorphic Hash
I. INTRODUCTION
Everything benefits from the sharing of information, things
are known because of it, and species continue because of it.
The birth and inheritance of human civilization is inseparable
from the sharing of information. In modern society, people are
spreading all sorts of information, either intentionally or
unintentionally. Such as short tweet, video and location
information and so on. Although the dissemination of
information is personal freedom, some information is
inconsistent with the law, and some of the information is
detrimental to personal privacy. Some information can be
broadcast, some information needs to be exchanged in person
or in close proximity, and some information needs to be
exchanged anonymously. Therefore, it is a worthwhile issue to
transmit specific information to specific recipients in a specific
manner [1]. In some scenarios where anonymous and secure
data exchange between strangers is required, it is ideal for
participants to run a Authentication Key Exchange (AKE)
protocol with bootstrapping trust.
AKE protocol can resist Man-in-the-middle Attacks,
Replay Attacks and Impersonation Attacks since mutual
authentication between participants. AKE has become very
popular in the Internet in the last few years. Unfortunately,
most of the existing AKE based on some Root of Trust or
Chain of Trust between the involved parties, such as prior
knowledge on a cryptographic key or password [2]-[7] or
Trusted Third Parties (TTP) [8][9]. In a P2P-like scenarios, the
above Unit of Trust (UoT) cannot be deployed. To address
these issues, many decentralized solutions are proposed[10]-
[12]. These schemes use key directories that store bindings
between identities and public keys to achieve consistency.
While these systems provide a reasonable user experience and
do not depend on any TTP, restricting parties can only use the
registered keys and thus complicating key management. In
particular, these schemes do not apply to scenarios where
strangers need to bootstrap trust. Dong et al. designed a secure
social proximity computation protocol [13], which can identify
potential friends on the premise of ensuring privacy, but it
requires TTP initialization parameters before running.
McCorry et al. proposed two protocols on the basis of ECDH
[14] and YAK [15], for secure communication between Bitcoin
users in a post-transaction scenario without requiring any TTP
or additional authentication credentials [16]. Bui et al. present a
family of key exchange protocols that utilizes the global
consistency property of the public ledgers [17]. These
protocols require secure out-of-band channel for sharing
parameters, when public identity are not available.
In this paper, we present a homomorphic hash and
Blockchain based AKE protocol (HBAKE), which can meet
the security needs and the computational demands of scenarios
that require strangers to bootstrap trust in an untrustworthy
environment. Multiple unfamiliar parties authenticate common
secret holders through Blockchain transactions and complete
the exchange of session keys on the promise of privacy
protection. The authentication here means identity
authentication of participants who hold the common secrets
and transaction-level certification of the key agreement process.
In this case, users who need to bootstrap trust use the common
interest event as a carrier to publish the hash value of the
common secret along with the tags corresponding to the secret
in the form of a Blockchain transaction. Any user with similar
needs can guess tags for the keyword initializing the Bloom
filter and searching for common interest events on the
Blockchain, if it is found that the holder of the common
interest event uses the homomorphic hash function value of the
common secret to construct the transaction leading to the
potential partner to initiate the common secret secure matching,
which ultimately calculates session secrets based on common
strings.
The rest of the paper is organized as follows. Section II
introduces the basics needed to understand this paper. We
describe the detail of our proposed scheme in Section III and
prove its security under the Standard Model. Section IV shows
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2018 Sixth International Conference on Advanced Cloud and Big Data
978-1-5386-8034-6/18/$31.00 ©2018 IEEE
DOI 10.1109/CBD.2018.00051