This book constitutes the refereed proceedings of the 19th International Conference on Cryptology in India, INDOCRYPT 2018, held in New Delhi, India, in December 2018. The 20 revised full papers presented in this book were carefully reviewed and selected from 60 submissions. The focus of the conference includes works on outsourced computation and searchable encryption; symmetric key cryptography and format preserving encryption; fault attacks and Hash functions; post quantum cryptography; asymmetric key cryptography and cryptanalysis; symmetric key cryptanalysis; theory; and secure computations and protocols.