Explore a comprehensive analysis of quantum security in CSIDH parameters and learn about attacking CSIDH quantumly in this 24-minute conference talk presented at Eurocrypt 2020. Delve into Chris Peikert's paper, which examines prior security estimates for CSIDH-512 and introduces the 'High Bits' Collimation Sieve. Understand the structure of the Collimation Sieve, including phase vectors, collimation procedures, and post-processing techniques such as regularization and measurement. Gain insights into practical issues and open questions surrounding this topic, ultimately concluding that proposed CSICH parameters may have relatively little quantum security.