Browse Prior Art Database

Memory Protection in Chip Cards

IP.com Disclosure Number: IPCOM000036605D
Original Publication Date: 1989-Oct-01
Included in the Prior Art Database: 2005-Jan-29
Document File: 2 page(s) / 46K

Publishing Venue

IBM

Related People

Scherzer, H: AUTHOR

Abstract

Presently, a plastic (credit) card for financial transactions may contain a microprocessor and a memory. The memory typically consists of a ROM with the operating system, a RAM acting as a working memory, and an additional EPROM (erasable programmable memory) or an EEPROM (electrically erasable programmable memory) for data to be loaded later. The EEPROM data may also be an application program that is loaded at a later stage.

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Memory Protection in Chip Cards

Presently, a plastic (credit) card for financial transactions may contain a microprocessor and a memory. The memory typically consists of a ROM with the operating system, a RAM acting as a working memory, and an additional EPROM (erasable programmable memory) or an EEPROM (electrically erasable programmable memory) for data to be loaded later. The EEPROM data may also be an application program that is loaded at a later stage.

For security applications, the card typically stores at least one master key which is eventually used to encrypt or decrypt data and which is referred to as a public key (PK) or a secret key (SK). Problem:

The chip card should allow loading the application program after the operating system has been created. The chip card is given to a third party that writes the application program and stores it on the chip card. The application program is able to read secret keys and the operating system code, as the microprocessor is fully controlled by the application program which later allows the microprocessor to force the program to disclose such keys in response to an "insider command". Solution:

The problem is checked by a security assurance party before it is written into the application memory EEPROM. This solution has the disadvantage that it involves extensive investigation work and that there is a great risk of undiscovered bad statements.

The memory to be protected is surveyed by an address decode unit. This un...