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The Implementation of Blind Signature in Digital Cash

Hariandi Maulid

Department of Informatics Engineering, School of Applied Science

Telkom University


Digital cash, an electronic or digital simulation of real cash, has been used widely to

buy or sell goods in the recent internet society. As it circulates via internet, all information

regarding transaction using digital cash can be recorded. Hence, the anonimity and privacy

become a serious concernto the payer and the payee. This paper will discuss how the

implementation of blind signature can preserve the anonimity and the privacy of all digital

cash user.


1. Introduction

Money plays an important role in the development of human history. The most

common form of money is shown as some actual objects, such as paper, argentine or gold.

All forms of money have the value which people can use to buy or sell goods. Nowadays,

digital cash, which represents money with both value and electronic form, has been widely

used in the recent society. It can be categorized by anonymous or identified, used online or


1.1 Digital cash

Digital cash, which is also called E-cash or E-money, was firstly produced by David

Chaum in 1982 [3]. It can be seen as the electronic or digital simulation of real cash. It

exists with the form of a series of encryption numbers, and circulates via the internet. This

series of encryption numbers can identify values of the real cash. Digital cash is developed

based on the development of Electronic Commerce.

Because of the particularity of internet and electronic form of digital cash, all the

information of transaction using digital cash can be recorded. How to guarantee the

anonymity and the privacy of the payer and payee has become the hottest research issue.

Therefore, it is important for digital cash to build a safe and feasible digital signature

scheme. By this reason, blind signature is invented.

1.2 Blind signature

Blind signature, which was firstly advanced by David Chaum in 1982 [3], is widely

used in the process of digital cash currently. It is a special form of digital signature. The

purpose of using blind signature is to protect the privacy of digital cash users. The

signature applicant uses blind signature to change the message which need to be signed,

then sends the "blind message" to the signatory, the signatory signs the message without

knowing the content of the message. By this way, the anonymity and the privacy of all the

digital cash users can be preserved.