This extended reunion is for long-term participants in the program Lattices: Algorithms, Complexity, and Cryptography, held in the spring 2020 semester. It will provide an opportunity to meet old and new friends. Moreover, we hope that it will give everyone a chance to reflect on the progress made during the semester and since, and sketch in which directions the field should go in the future. In an effort to keep things informal and to encourage open discussion, none of the activities will be recorded. Participation in the reunion is by invitation only.

The study of integer lattices serves as a bridge between number theory and geometry and has for centuries received the attention of illustrious mathematicians, including Lagrange, Gauss, Dirichlet, Hermite, and Minkowski. In computer science, lattices made a grand appearance in 1982 with the celebrated work of Lenstra, Lenstra, and Lovász, who developed the celebrated LLL algorithm to find short vectors in integer lattices. The role of lattices in cryptography has been equally, if not more, revolutionary and dramatic, with lattices first playing a destructive role as a potent tool for breaking cryptosystems and later serving as a new way to realize powerful and game-changing notions such as fully homomorphic encryption. These exciting developments over the last two decades have taken us on a journey through such diverse areas as quantum computation, learning theory, Fourier analysis, and algebraic number theory. 

The program Lattices: Algorithms, Complexity, and Cryptography was supported in part by the Alfred P. Sloan Foundation.