This book constitutes the proceedings of the 6th International Conference on Cryptology and Security in Latin America, LATINCRYPT 2019, held in Santiago di Chile, Chile, in October 2019. The 18 revised full papers presented were carefully reviewed and selected from 40 submissions. The papers are organized in topical sections on cryptoanalysis, symmetric cryptography, ide-channel cryptography, post-quantum cryptography, signatures and protocols, and implementation.