Cryptology ePrint Archive: Report 2015/170

Stealing Keys from PCs using a Radio: Cheap Electromagnetic Attacks on Windowed Exponentiation

Daniel Genkin and Lev Pachmanov and Itamar Pipman and Eran Tromer

Abstract: We present new side-channel attacks on RSA and ElGamal implementations that use the popular sliding-window or fixed-window (m-ary) modular exponentiation algorithms. The attacks can extract decryption keys using a very low measurement bandwidth (a frequency band of less than 100 kHz around a carrier under 2 MHz) even when attacking multi-GHz CPUs.

We demonstrate the attacks' feasibility by extracting keys from GnuPG, in a few seconds, using a nonintrusive measurement of electromagnetic emanations from laptop computers. The measurement equipment is cheap and compact, uses readily-available components (a Software Defined Radio USB dongle or a consumer-grade radio receiver), and can operate untethered while concealed, e.g., inside pita bread.

The attacks use a few non-adaptive chosen ciphertexts, crafted so that whenever the decryption routine encounters particular bit patterns in the secret key, intermediate values occur with a special structure that causes observable fluctuations in the electromagnetic field. Through suitable signal processing and cryptanalysis, the bit patterns and eventually the whole secret key are recovered.

Category / Keywords: side channel, electromagnetic analysis, RSA, ElGamal

Date: received 27 Feb 2015, last revised 3 Mar 2015

Contact author: tromer at cs tau ac il

Available format(s): PDF | BibTeX Citation

Note: Revised March 3, 2015: minor editorial changes.

Version: 20150303:085429 (All versions of this report)

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