This book constitutes the refereed proceedings of the Cryptographers' Track at the RSA Conference 2010, CT-RSA 2010, held in San Francisco, CA, USA in April 2010. The 25 revised full papers presented together with 1 invited lecture were carefully reviewed and selected from 94 submissions. The papers are organized in topical sections on public-key cryptography, side-channel attacks, cryptographic protocols, cryptanalysis, and symmetric cryptography.