Learn about a key recovery attack on QC-MDPC codes with CCA security in this 23-minute conference talk from Asiacrypt 2016. Explore the motivation behind QC-MDPC codes, their use in public-key cryptography, and the CCA-secure version. Delve into iterative decoding using Gallager's bit-flipping strategy and understand the key-related property of distance spectrum. Examine the main observation and attack scenarios for both plain QC-MDPC and CCA-secure QC-MDPC. Gain insights into the distinguishing procedure, results for obtaining distance spectrum in the CPA case, and final remarks on this cryptographic research.