diff --git a/.DS_Store b/.DS_Store index 8ea9f01..2a91c29 100644 Binary files a/.DS_Store and b/.DS_Store differ diff --git a/unit02_symmetric/.DS_Store b/unit02_symmetric/.DS_Store index 579d649..2553aff 100644 Binary files a/unit02_symmetric/.DS_Store and b/unit02_symmetric/.DS_Store differ diff --git a/unit02_symmetric/lecture/chapter02_secret.pptx b/unit02_symmetric/lecture/chapter02_secret.pptx index a1aeed4..05372ec 100644 Binary files a/unit02_symmetric/lecture/chapter02_secret.pptx and b/unit02_symmetric/lecture/chapter02_secret.pptx differ