This paper exposes some weaknesses of encrypted embedded memory in secure chips. Smartcards and secure microcontrollers are designed to protect confidential internal information. For that they widely employ on-chip memory encryption. Usually both data and address buses are encrypted to prevent microprobing attacks. This paper shows how practical such attacks can be on real chips and whether memory encryption is as good as it is supposed to be. It was possible to extract the whole memory from a secure 8-bit microcontroller with as little as 8 probing needles. This paper questions the usual belief in that ion-doping-encoded and encrypted Mask ROM is ultimately secure. Implications for 16-bit and 32-bit microcontrollers are discussed as well. Some common weaknesses are exposed and possible countermeasures are discussed.

This paper introduces some new types of optical fault attacks called fault masking attacks. These attacks are aimed at disrupting of the normal memory operation through preventing changes of the memory contents. The technique was demonstrated on an EEPROM and Flash memory inside PIC microcontrollers. Then it was improved with a backside approach and tested on a PIC and MSP430 microcontrollers. These attacks can be used for the partial reverse engineering of semiconductor chips by spotting the areas of activity in reprogrammable non-volatile memory. This can assist in data analysis and other types of fault injection attacks later, thereby saving the time otherwise required for exhaustive search. Practical limits for optical fault masking attacks in terms of sample preparation, operating conditions and chip technology are discussed, together with possible countermeasures.