A new class of attacks on secure microcontrollers and smartcards, called optical fault induction attacks, has been described. These attacks use light to induce faults in transistors, causing them to conduct and thereby inducing transient faults. The attacks are practical and can be carried out using inexpensive equipment, such as a flashgun and a laser pointer. The authors demonstrated that it is possible to set or reset any individual bit of SRAM in a microcontroller using this method. Optical probing can also be used to induce errors in cryptographic computations or protocols, and to disrupt the processor's control flow. This vulnerability poses a significant problem for the industry, similar to those resulting from probing attacks in the mid-1990s and power analysis attacks in the late 1990s. To counter these attacks, the authors developed a technology based on self-timed dual-rail circuit design. This technique uses pairs of lines to encode logical 1 or 0, with (HL) or (LH) representing 0 or 1, respectively. The combination (HH) signals an alarm, which will typically reset the processor. Circuits can be designed so that single-transistor failures do not lead to security failure. This technology may also make power analysis attacks much harder. The authors also demonstrated that optical probing attacks can be carried out using low-cost equipment. They used a photoflash lamp and a laser pointer to change the state of individual SRAM cells. The results showed that it is possible to change any individual bit of an SRAM array. The authors also showed that the addresses of memory cells can be mapped using this technique. The implications of these attacks are significant. They show that optical probing attacks are possible using low-cost equipment. The authors also recommend that designers of ICs should study their designs carefully to ensure that there are no single-transistor failures that can subvert the chip's security policy. The authors have also developed countermeasures to protect against these attacks. These countermeasures include self-timed dual-rail logic, which is more robust against single-transistor failures. The authors believe that such robustness will be a requirement for many high-security devices in the future.A new class of attacks on secure microcontrollers and smartcards, called optical fault induction attacks, has been described. These attacks use light to induce faults in transistors, causing them to conduct and thereby inducing transient faults. The attacks are practical and can be carried out using inexpensive equipment, such as a flashgun and a laser pointer. The authors demonstrated that it is possible to set or reset any individual bit of SRAM in a microcontroller using this method. Optical probing can also be used to induce errors in cryptographic computations or protocols, and to disrupt the processor's control flow. This vulnerability poses a significant problem for the industry, similar to those resulting from probing attacks in the mid-1990s and power analysis attacks in the late 1990s. To counter these attacks, the authors developed a technology based on self-timed dual-rail circuit design. This technique uses pairs of lines to encode logical 1 or 0, with (HL) or (LH) representing 0 or 1, respectively. The combination (HH) signals an alarm, which will typically reset the processor. Circuits can be designed so that single-transistor failures do not lead to security failure. This technology may also make power analysis attacks much harder. The authors also demonstrated that optical probing attacks can be carried out using low-cost equipment. They used a photoflash lamp and a laser pointer to change the state of individual SRAM cells. The results showed that it is possible to change any individual bit of an SRAM array. The authors also showed that the addresses of memory cells can be mapped using this technique. The implications of these attacks are significant. They show that optical probing attacks are possible using low-cost equipment. The authors also recommend that designers of ICs should study their designs carefully to ensure that there are no single-transistor failures that can subvert the chip's security policy. The authors have also developed countermeasures to protect against these attacks. These countermeasures include self-timed dual-rail logic, which is more robust against single-transistor failures. The authors believe that such robustness will be a requirement for many high-security devices in the future.