Announcements:Announcements:1.1. Presentations start next ThursdayPresentations start next Thursday

Questions? Questions?

This week and Monday:This week and Monday: DSA, Digital CashDSA, Digital Cash

DTTF/NB479: DszquphsbqizDTTF/NB479: Dszquphsbqiz Day 32Day 32

DSA SLIDES MOVED TO DSA SLIDES MOVED TO PRIOR SLIDE SETPRIOR SLIDE SET

Show me the money!Show me the money!

Digital cash (chapter 11)Digital cash (chapter 11)

Want it to be electronic, like a credit card.Want it to be electronic, like a credit card.

But what’s so attractive about cash (vs. a But what’s so attractive about cash (vs. a credit card)?credit card)?

Digital Cash: goalsDigital Cash: goals

Electronic: want speed and securityElectronic: want speed and security

Can’t be counterfeitedCan’t be counterfeited Can a central bank just track electronic Can a central bank just track electronic

notes? notes? Then not anonymous!Then not anonymous! Neither could transactions be done offlineNeither could transactions be done offline

Digital Cash: goalsDigital Cash: goals

Electronic: want speed and securityElectronic: want speed and security

Can’t be counterfeitedCan’t be counterfeited

Anonymous: spender’s ID not disclosed to Anonymous: spender’s ID not disclosed to merchantmerchant

Payment done offlinePayment done offline

TransferableTransferable

Divisible (can make change)Divisible (can make change)

Okimoto and Ohta: Universal electronic cash, In Proc. Advances in Computing – CRYPTO, 1991