This book constitutes the refereed proceedings of the Second International Conference, ICSP 2021, held in Jamshedpur, India, in November 2021. The 10 full papers were carefully reviewed and selected from 44 submissions. The contributions are organized in the following blocks: Cryptanalysis and other attacks; Symmetric cryptography and hash functions; Mathematical foundations of cryptography; Embedded systems security; Security in hardware; Authentication, Key management, Public key (asymmetric) techniques, and Information-theoretic techniques.