AN2646 datasheet(25/43 Pages) STMICROELECTRONICS

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AN2646 - Application note

ISO 7816-4 – smartcard commands

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Verify

This command is sent by the application on the reader side to the security system on the

card. Its purpose is to convince the card that the reader knows a password maintained by

the card in order to restrict access to sensitive information stored on the card. The

password-type information may be associated with a specific file or to some or all of the file

hierarchy. If the Verify command fails i.e. the reader provides an incorrect password, an error

is returned to the reader.

Internal Authenticate

This command allows the card to authenticate itself to the reader by proving that it

possesses a secret key shared with the reader. The reader application software first

generates a random number and encrypts it with some algorithm known to both card and

reader. This constitutes a challenge to the card. The card then decrypts this challenge with

the secret key (that is stored on the card) and sends the resulting data back to the reader. If

the data received by the reader matches the random number that it generated then the

reader application software is assured of the identity of the card.

External Authenticate

This command is used in conjunction with the Get Challenge command to enable the reader

application software to authenticate itself to the card. The reader receives challenge data (a

random number) from the card and encrypts it with a secret key. This is then sent to the card

using the External Authenticate command. The card decrypts the data and compares it to

the random number that it generated in the previous Get Challenge command. If there is a

match, then the card is assured of the identity of the reader application.

Get Challenge

This command is sent by the reader to the card. Its purpose is to provide the reader

application with a random number generated by the smartcard. As previously described, this

number is used in the External Authenticate command.

Manage Channel

The Manage Channel command is used by the reader application to open and close the

logical communication channels between it and the card. Initially the card opens a basic

communication channel by establishing an application-level protocol with the reader

application through the completion of an ATR sequence. This channel is then used to open

or close additional logical channels through the Manage Channel command.

Envelope

This command supports the use of secure messaging using the T0 protocol. It enables an

APDU to be encrypted and then incorporated into the Envelope command's data section (of

its APDU). The APDU processor on the card can then extract and execute the command.

Get Response

As with the previous command, the Get Response command allows the use of the T0

protocol for transferring APDUs. The Case 4 type of APDU cannot be supported by the T0

protocol i.e. it is not possible to send a block of data to the card and then receive a block of

data in return. So when using the T0 protocol, the initial command results in a response

which indicates that more data is waiting to be sent by the card. The Get Response

command is then used to retrieve this data.

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