sẽ có hơn 280 triệu đỉnh được kết nối bởi một trang web tinh rối của các cạnh. Mạng máy tính này rất giống với các mạng xã hội và có thể được đại diện bởi đồ thị trong một cách tương tự. Trong thực tế, bạn đã có thể nhìn thấy một đồ thị | Peer to Peer Harnessing the Power of Disruptive Technologies Micropayment digital cash schemes Ronald Rivest and Adi Shamir introduced two simple micropayment schemes PayWord and MicroMint in 1996. 16 PayWord is a credit-based scheme based on chains of paywords hash values while MicroMint represents coins by k -way hash function collisions. Both of these schemes follow the lightweight philosophy of micropayments nickels and dimes don t matter. If a user loses a payment or is able to forge a few payments we can ignore such trivialities. The security mechanisms in these schemes are not as strong nor expensive as the full macropayment digital cash schemes we will discuss later. At a rough estimate hashing is about 100 times faster than RSA signature verification and about 10 000 times faster than RSA signature generation. 16 R. Rivest and A. Shamir 1997 PayWord and MicroMint Two Simple Micropayment Schemes Lecture Notes in Computer Science vol. 1189 Proc. Security Protocols Workshop Springer-Verlag pp. 69-87. PayWord is designed for applications in which users engage in many repetitive micropayment transactions. Some examples are pay-per-use web sites and pay-per-minute online games or movies. PayWord relies on a broker better known as a bank in many digital cash schemes mainly for online verification but seeks to minimize communication with the broker in order to make the system as efficient as possible. It works like this. Alice establishes an account with a broker and is issued a digital certificate. When she communicates with vendor Bob for the first time each day she computes and commits to a new payword chain wi w2 . wn. This chain is created by choosing some random wn and moving backward to calculate each hash wi from the hash wi 1. Alice starts her relationship with Bob by offering w0. With each micropayment she moves up the chain from w0 toward wn. Just knowing w0 vendor Bob can t compute any paywords and therefore can t make false claims to the .
