4.4 Methods of Implementation of Hardware Trojans …
331
At the gate level, the microcircuit design is presented as a description of the
interrelation of library logic gates. This level allows the “hacker” to carefully control
all aspects of the introduced Trojan, including its size and location.
Basic (standard) libraries of transistors are usually used to build “infected” logic
gates. If a Trojan is introduced at this level, its developer gains full control over such
important characteristics of the microcircuit as power consumption and performance.
As circuit engineers know, individual transistors can be inserted or removed without
changing the basic functionality of a microcircuit [136]. The sizes of the transistor
can also be unauthorized to modify and thereby change the basic parameters of the
microcircuit, for example, to reduce its reliability or speed [137].
At the topological level, microcircuit designers usually describe the geometric
characteristics and the relationship between all the components of the microcircuit. It
should be highlighted that this is the specific stage of the route where Trojans are most
often introduced, but Trojans, for example, can be installed by making unauthorized
changes in the size of wiring diagrams, changes in the distance between the circuit
elements, and by redistributing metal wiring layers.
4.5 Mechanisms for Activating Introduced Hardware
Trojans
As a rule, after completing the process of introduction into the system (microcircuit),
the hardware Trojan is at complete rest (sleep mode) until it is activated (launched)
to perform its targeted malicious function.
The activation mechanisms of Trojans can be of the most diverse nature (explicit or
hidden, random, direct, or predetermined), as a result of which the hardware Trojan
can change its state and behavior. Knowledge of these mechanisms is extremely
important both for the microcircuit designer and the Trojan hunter, since the activation
process itself can carry additional (indirect) information that allows an experienced
cybersecurity expert to identify and counteract the hardware Trojan. An additional
difficulty in organizing the process of “hunting Trojans” lies in the qualification
requirements and experience of the “hunter.” After all, in addition to specific knowledge in the field of information security, he must be well versed in all the nuances of
microelectronic technologies and in the features of all stages of the complex route of
designing modern microcircuits. Better yet, the “hunter” himself should have practical experience in the design and technological support of lots of plates in the mass
production of microcircuits.
If the project manager for creating a high-duty microcircuit does not have such
a universal specialist, then an entire team of narrowly focused specialist should
participate in this “hunt” under the unified leadership of the “chief hunter.”
Therefore, experienced “hunters” recommend trying to activate such introduced
hardware Trojans already at the stages of IC verification. This is usually done during
331
At the gate level, the microcircuit design is presented as a description of the
interrelation of library logic gates. This level allows the “hacker” to carefully control
all aspects of the introduced Trojan, including its size and location.
Basic (standard) libraries of transistors are usually used to build “infected” logic
gates. If a Trojan is introduced at this level, its developer gains full control over such
important characteristics of the microcircuit as power consumption and performance.
As circuit engineers know, individual transistors can be inserted or removed without
changing the basic functionality of a microcircuit [136]. The sizes of the transistor
can also be unauthorized to modify and thereby change the basic parameters of the
microcircuit, for example, to reduce its reliability or speed [137].
At the topological level, microcircuit designers usually describe the geometric
characteristics and the relationship between all the components of the microcircuit. It
should be highlighted that this is the specific stage of the route where Trojans are most
often introduced, but Trojans, for example, can be installed by making unauthorized
changes in the size of wiring diagrams, changes in the distance between the circuit
elements, and by redistributing metal wiring layers.
4.5 Mechanisms for Activating Introduced Hardware
Trojans
As a rule, after completing the process of introduction into the system (microcircuit),
the hardware Trojan is at complete rest (sleep mode) until it is activated (launched)
to perform its targeted malicious function.
The activation mechanisms of Trojans can be of the most diverse nature (explicit or
hidden, random, direct, or predetermined), as a result of which the hardware Trojan
can change its state and behavior. Knowledge of these mechanisms is extremely
important both for the microcircuit designer and the Trojan hunter, since the activation
process itself can carry additional (indirect) information that allows an experienced
cybersecurity expert to identify and counteract the hardware Trojan. An additional
difficulty in organizing the process of “hunting Trojans” lies in the qualification
requirements and experience of the “hunter.” After all, in addition to specific knowledge in the field of information security, he must be well versed in all the nuances of
microelectronic technologies and in the features of all stages of the complex route of
designing modern microcircuits. Better yet, the “hunter” himself should have practical experience in the design and technological support of lots of plates in the mass
production of microcircuits.
If the project manager for creating a high-duty microcircuit does not have such
a universal specialist, then an entire team of narrowly focused specialist should
participate in this “hunt” under the unified leadership of the “chief hunter.”
Therefore, experienced “hunters” recommend trying to activate such introduced
hardware Trojans already at the stages of IC verification. This is usually done during