A system and a method transmits the electronic coupon to a personal digital assistant ("PDA"), for use. Prior to transmitting the electronic coupon, the computer may encrypt the electronic coupon. A consumer next displays the electronic coupon on the PDA to a merchant and the merchant gives the appropriate...http://www.google.es/patents/US20020128903?utm_source=gb-gplus-sharePatente US20020128903 - ENCRYPTED COUPONS
