A local EM-analysis attack resistant cryptographic engine with fully-digital oscillator-based tamper-access sensor

A cryptographic engine (CE) resistant to local EM-analysis attacks (L-EMAs) is developed. An LC-oscillator-based tamper-access sensor detects a micro EM-probe approach and therefore protects the secret key information. A fully-digital sensor circuit with a reference-free dual-coil sensing scheme and a ring-oscillator-based one-step digital sensor calibration reduces the sensor area overhead to 1.6%. The sensor intermittently operates in interleave between CE operations, which saves power and performance penalty to 7.6% and 0.2%. A prototype in 0.18µm CMOS successfully demonstrates L-EMA attack detection and key protection for the first time.