Since the 0.9 Hydrogen Helix version, Payment IDs can be encrypted and embedded in a payment address. The Payment IDs of this type should be 64-bits and are encrypted with a random one-time key known only to the sender and receiver.
It is recommended to use the official wallet's `integrated_address` command to automatically generate Integrated Addresses that contain Compact Payment IDs. If you want to use the command line, you can generate Payment IDs as follows: