High Density Smart Cards: New Security Challenges and Applications

Abstract

High Density cards represent the next generation of secure portable and removable tokens for the mobile and wireless markets. What makes these cards so particular is that, in addition to the traditional ISO 7816 interface to the Subscriber Identity Module, there are hundreds of megabytes of non-volatile Flash Memory available on the same token. This is a small revolution when compared to current EEPROM cards which allow for only a few hundreds of kilobytes of memory both for applications and data. Flash memory can be accessed either via a USB (Universal Serial Bus) or an MMC (MultiMediaCard) high speed interface. Therefore two different ecosystems co-exist on the same chip, which makes the security aspects of these cards particularly interesting and challenging.

In this paper we examine the specific security aspects of such high density cards and explain what potential security issues a manufacturer has to face and how he can overcome them. We discuss specifically how flash memory interacts with other memory on board, how it is organised, what it is used for. We contrast this approach with the memory architecture and organization of conventional smart cards such as those used in GSM and EMV payment applications. Since there is no ROM memory at all on these cards, we explain where the proprietary and highly sensitive operating system of the card manufacturer and the proprietary algorithms of the telecommunications operators will reside, how they can be protected and what the challenges are for initializing the whole system. Current secure smart card personalization techniques will have to be revisited and new procedures need to be put in place to securely instantiate this new generation of (SIM) cards. New algorithms for EEPROM emulation and anti-tearing (the fact that data is not lost when power is lost abruptly) need to be developped, one-time programmable areas need to be provided to boot-up securely. Initial program loader techniques and public key schemes are required for secure personalization. The high speed interface has to be secured and separated from access to the main memory on chip.

We also discuss security aspects of single die architectures, platform security for flash memory cards and security aspects of cryptographic hardware cores including the necessity to protect them against side-channel attacks as on traditional smart cards. These security features in turn allow considering high density cards for enhanced security applications such as secure data storage thanks to on-the-fly encryption at the megabyte rate, enterprise DRM, DRM agents for mobile TV, mobile payment and m-commerce. New applications which require huge storage capacity and sophisticated security features at the same time are enabled with this new generation of smart removable devices.