Sivupolkuhyökkäys

Sivupolkuhyökkäys, also known as side-channel attack, is a type of security exploit that relies on information gained from the physical implementation of a cryptosystem, rather than theoretical weaknesses in the algorithm itself. This information can include the time taken to perform computations, power consumption, electromagnetic emissions, or sound produced. Attackers analyze these physical characteristics to deduce sensitive information, such as secret keys.

One common type of sivupolkuhyökkäys is timing attacks. These exploit the fact that different operations in a cryptographic algorithm might take slightly different amounts of time to execute. By precisely measuring these execution times, an attacker can infer information about the data being processed. For example, if a comparison operation takes longer when a bit is 1 than when it is 0, an attacker can determine the value of individual bits of a secret key by repeatedly observing the execution time.

Power analysis attacks are another significant category. These involve monitoring the power consumption of a device as it performs cryptographic operations. Different instructions and operations consume varying amounts of power, and these variations can be correlated with the data being processed. Simple power analysis (SPA) directly analyzes the power trace, while differential power analysis (DPA) uses statistical methods to extract more subtle information by averaging many traces.

Electromagnetic (EM) attacks exploit the electromagnetic radiation emitted by electronic devices during operation. Similar to power consumption, these emissions can vary based on the operations being performed and the data being processed. Sound analysis attacks, though less common, can also be used by analyzing the acoustic emissions from components like capacitors or coils.

Defenses against sivupolkuhyökkäykset often involve making cryptographic implementations more uniform and less distinguishable. Techniques include constant-time execution, where all operations take the same amount of time regardless of the data, and power or EM shielding to reduce leakage. Randomization of operations and the introduction of noise can also help obscure the signal from the attacker.