Preventing Simple and Differential Power Analysis Attacks
Power analysis attacks cannot generally be detected by a device, since the adversary's monitoring is normally passive. In addition, the attack is non-invasive. As a result, physical enclosures, auditing capabilities, and attack detectors are ineffective. Instead, cryptosystem engineers must ensure that devices' power variations do not reveal information usable by adversaries.
Simple power analysis can easily distinguish the outcome of conditional branches in the execution of cryptographic software, since a device does different things (consuming different power) depending on whether the conditional branch is taken. For this reason, care should be taken to ensure there are no secret values which affect the conditional branches within cryptographic software implementations. Other sources of variation, such as microcode differences, branches introduced by compilers, and power consumption variations in multipliers, also commonly lead to SPA vulnerabilities.
Differential power analysis is more difficult to prevent, since even small biases in the power consumption can lead to exploitable weaknesses. Some countermeasure strategies involve algorithmic modifications such that the cryptographic operations occur on data that is related to the actual value by some mathematical relationship that survives the cryptographic operation. One approach involves blinding parameters to randomize their value. Other countermeasure strategies to reduce the effectiveness of DPA attacks involve hardware modifications: varying the chip internal clock frequency has been considered to desynchronize electric signals, which lead in return to algorithmic enhancements of traditional DPA.,
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