Smart cards, what are they, what is their function and what are they used for

If you have ever wondered how the chip works inside your mobile’s SIM card, your mobile’s credit card or the electronic key of the last hotel you stayed in. Let us tell you that all of them are smart cards and have a common function.

What is a smart card?

A smart card is a plastic card that has an integrated circuit inside. Said integrated circuit can be a security microcontroller with or without internal memory or include only one memory chip. All smart cards can be connected to a dedicated reader to be able to read their data or via contactless via a dedicated radio interface.

Smart cards have the following utilities:

• They are used for credit or debit cards.
• SIM cards of different types in smartphones are smart cards.
• Staff cards in many companies, which allow them to punch in and out.
• They are used to provide secure access to private networks.
• As a system to prevent piracy of cable and satellite TV services. Currently on the verge of extinction.

How does a smart card work?

Most Smart Cards are memory cards, so they do not contain an integrated microcontroller and require the reader to directly process the data included on the card, however there are variants whose integrated circuit contains a microcontroller, which in many case replaces the classic magnetic tape they used

The microcontroller contained in smart cards is no different from any other microcontroller on the market. Which integrates several KB of RAM memory, several tens of KB of ROM memory already recorded at the start and several KB of programmable ROM memory in the same material.

Depending on the type of application and the sensitivity of the data, a microcontroller will be implemented or not, whose task is to ensure that the data included in the memory of the card is not accessed illegally.

How does a smart card communicate?

No matter what type of hardware we are talking about, smart cards communicate using 7 different pins. Which are the following:

• VCC: Since smart cards don’t have power inside, they need the card reader to power the card. It does so through this type with a voltage of +5 V DC.
• GND: Grounding.
• CLOCK: The clock signal of the Smart Card, marks the pulse at which the data is sent.
• Vice-president: The programming voltage is used to manipulate the data in the programmable ROM, whether to add new, delete or overwrite it.
• I / O: The pin through which data is transmitted to and from the smart card. Being a single pin, we are faced with a serial interface.
• Some smart cards have two additional pins to communicate with a USB interface external. Although not all smart cards have these pins active and they are only used in specific cases.

How is memory organized on a smart card?

Certain smart cards, comprising a microcontroller inside, therefore have a RAM memory so that said microcontroller can operate. This memory is called Trabajo ram o working ram and like conventional RAM this depends on the board receiving powerTherefore, once the smart card is removed from the reader, your data will be lost permanently.

In addition to the functional RAM, smart cards with microcontroller contain a ROM where the operating system is located. This ROM is several kilobytes and tthe various encryption and security algorithms that are executed by the microcontroller are encoded inside and which are essential for certain applications. The RAM is read-only and is integrated into the smart card during manufacture, e.g.or your data cannot be modified.

Inside the ROM there is an area called the Secret ROM, this includes highly sensitive information, among the data that is typically stored are the following:

• The unique manufacturer key, which exists only one for each card manufactured and will be used for the encryption and decryption exercises performed by the microcontroller of the card.
• the user keys, which contains the PIN code of the credit card or mobile phone. In some models of smart cards, this data is located in programmable ROM. Which makes them less secure.
• One secret code, which serves to avoid duplicates and falsifications of the card.

The last memory is programmable ROM, it is a type of ROM that can be rewritten via electrical signals. We are therefore faced with an EEPROM memory. Not all smart card readers have the capability to handle programmable ROM, but others do. For example, an ATM has this capability, but a simple USB drive does not have this capability.

Types of smart card

Currently, we can find two types of smart cards used daily by hundreds of millions of people around the world.

The first type of smart cards are those that follow the ISO 7816 standard, but are memory cards and can contain inside a programmable ROM between 1 Kbit and 1 Mbit of information which can be programmed via an EEPROM I2C interface, of which between 3 Kbit-64 Kbits corresponds to the secure segment which is not accessible by the interface. Among those that follow ISO 7816 are the Smart cards with integrated microcontroller. In this case, the information your programmable ROM can store is usually no more than the 144 KB, since it is necessary to leave room for the microcontroller.

The third type is Contactless cards, which do not use ISO 7816 and they often use proprietary protocols for data transfer. These cards transmit data through an ultra-high frequency wireless radio interface, so they do not require connection to a card reader and do not use pins for communication.

And finally, we have those that have specialized microcontrollers built in for different types and have much more specific and concrete utilities. These include fingerprint reading systems and biometric systems for fluid analysis. They therefore also have applications in medicine, although these are apparently different from classic Smart Cards, their operation is the same.