Enjoyrfid Technical

In December 2004, EPC Global, the association that sets standards for bar codes and RFID tags, issued its second-generation UHF standard, Class 1 Gen 2. It unifies the air-interface protocols readers use to communicate with tags. Proponents predict it will speed development of cheaper hardware and spread UHF technology worldwide. 
Gen 2 also: 

Provides four communication speeds that maximize throughput of multiple tag reads under adverse conditions, and under strict regulations in Europe and Asia. The previous generation's one-size-fits-all speed didn't adapt as well to varying conditions. Gen 2 nearly quadruples the number of possible tag reads per second.

Improves reading of tags at the edge of transmission range.

Expands tag ID size from 96 to 512 bits, though users are experimenting with tags that hold hundreds of kilobits, industry sources said.

Introduces a 'dense-reader' mode that improves read rates of multiple readers in close proximity.

Tightens security by raising the number of bits available in passwords for deactivating tags from 8 to 32 bits; allowing tags to generate hard-to-crack, 16-bit random numbers; and scrambling reader signals to make it 'virtually impossible' for intruders to read tag numbers, said EPC Global.

In the future, systems such as larger-memory tags, better security and battery-backed active tags with sensors will be possible through planned Class 2 and 3 updates, according to the organization. 

Critics supporting competing HF cards insist, however, that Gen 2 still doesn't support the encryption and random numbers needed for secure passwords.