Nope, an EM4100-compatible card (or a key fob) is just a 64-bit ROM with radio interface. You can read its value and replay it to a reader; the latter won't be able to tell the difference between the original card and your spoofed one. Better (and more expensive) RFID tags may have an encrypted communication protocol.

Are all RFID cards the same?

Not all RFID cards are the same. There are two types of cards: RFID contactless cards with 125KHz and 13.56Mhz frequency chips. The first type of chip is called Low Frequency (LF), second – High Frequency (HF).

Can any RFID reader read any tag?

RFID Tag Technology

In most instances, each type of passive RFID tag (LF, HF, or UHF) can only be read by the SAME type of passive RFID reader. For instance, usually an LF reader will only be able to read an LF tag; it will not able to read an HF or a UHF tag.