This book constitutes the refereed proceedings of the Cryptographer's Track at the RSA Conference 2017, CT-RSA 2017, held in San Francisco, CA, USA, in February 2017. The 25 papers presented in this volume were carefully reviewed and selected from 77 submissions. CT-RSA has become a major publication venue in cryptography. It covers a wide variety of topics from public-key to symmetric key cryptography and from cryptographic protocols to primitives and their implementation security. This year selected topics such as cryptocurrencies and white-box cryptography were added to the call for papers.