Do not forget: NSA Created Bitcoin and the Blockchain: groups.csail.mit.edu/mac/classes/6.805/articles/money/nsamint/nsamint.htm - - - - HOW TO MAKE A MINT: THE CRYPTOGRAPHY OF ANONYMOUS ELECTRONIC CASH Laurie Law, Susan Sabett, Jerry Solinas National Security Agency Office of Information Security Research and Technology Cryptology Division 18 June 1996 CONTENTS INTRODUCTION 1.WHAT IS ELECTRONIC CASH? 1.1 Electronic Payment 1.2 Security of Electronic Payments 1.3 Electronic Cash 1.4 Multiple Spending 2.A CRYPTOGRAPHIC DESCRIPTION 2.1 Public-Key Cryptographic Tools 2.2 A Simplified Electronic Cash Protocol 2.3 Untraceable Electronic Payments 2.4 A Basic Electronic Cash Protocol 3.PROPOSED OFF-LINE IMPLEMENTATIONS 3.1 Including Identifying Information 3.2 Authentication and Signature Techniques 3.3 Summary of Proposed Implementations 4.OPTIONAL FEATURES OF OFF-LINE CASH 4.1 Transferability 4.2 Divisibility 5.SECURITY ISSUES 5.1 Multiple Spending Prevention 5.2 Wallet Observers 5.3 Security Failures 5.4 Restoring Traceability CONCLUSION REFERENCES Electronic payment systems come in many forms including digital checks, debit cards, credit cards, and stored value cards. The usual security features for such systems are privacy (protection from eavesdropping), authenticity (provides user identification and message integrity), and nonrepudiation (prevention of later denying having performed a transaction) . The type of electronic payment system focused on in this paper is electronic cash. As the name implies, electronic cash is an attempt to construct an electronic payment system modelled after our paper cash system. Paper cash has such features as being: portable (easily carried), recognizable (as legal tender) hence readily acceptable, transferable (without involvement of the financial network), untraceable (no record of where money is spent), anonymous (no record of who spent the money) and has the ability to make "change." The designers of electronic cash focused on preserving the features of untraceability and anonymity. Thus, electronic cash is defined to be an electronic payment system that provides, in addition to the above security features, the properties of user anonymity and payment untraceability.. - - - -