Building a Payment Applet on Java Card: From JCOP4 to EMV Contactless

Java Card is the platform that runs inside billions of smart cards worldwide. If you've ever tapped a Visa or Mastercard, you've interacted with a Java Card applet. We built our own. Here's what that looks like. What Is Java Card? Java Card is a stripped-down Java environment designed for smart cards and secure elements. It runs on chips with: 1-5 KB RAM 32-128 KB EEPROM 8-32 bit processors Despite these constraints, it supports cryptographic operations, secure storage, and the