1. Announcements: 1. Presentations start next Thursday Questions? This week and Monday: DSA, Digital Cash DSA, Digital Cash DTTF/NB479: DszquphsbqizDay 32

2. DSA SLIDES MOVED TO PRIOR SLIDE SET

3. Show me the money!

4. Digital cash (chapter 11) Want it to be electronic, like a credit card. But what’s so attractive about cash (vs. a credit card)?

5. Digital Cash: goals Electronic: want speed and security Can’t be counterfeited Can a central bank just track electronic notes? Can a central bank just track electronic notes? Then not anonymous! Then not anonymous! Neither could transactions be done offline Neither could transactions be done offline

6. Digital Cash: goals Electronic: want speed and security Can’t be counterfeited Anonymous: spender’s ID not disclosed to merchant Payment done offline Transferable Divisible (can make change) Okimoto and Ohta: Universal electronic cash, In Proc. Advances in Computing – CRYPTO, 1991