diff --git a/unit02_symmetric/lecture/~$chapter02_secret.pptx b/unit02_symmetric/lecture/~$chapter02_secret.pptx deleted file mode 100644 index b71c76f..0000000 Binary files a/unit02_symmetric/lecture/~$chapter02_secret.pptx and /dev/null differ diff --git a/unit03_hashing/lecture/~$chapter03_hashing_authentication.pptx b/unit03_hashing/lecture/~$chapter03_hashing_authentication.pptx deleted file mode 100644 index b71c76f..0000000 Binary files a/unit03_hashing/lecture/~$chapter03_hashing_authentication.pptx and /dev/null differ diff --git a/unit04_public_key/lecture/~$chapter04_public_msc.pptx b/unit04_public_key/lecture/~$chapter04_public_msc.pptx deleted file mode 100644 index b71c76f..0000000 Binary files a/unit04_public_key/lecture/~$chapter04_public_msc.pptx and /dev/null differ