diff --git a/SDR.md b/SDR.md
new file mode 100644
index 0000000..f31ac38
--- /dev/null
+++ b/SDR.md
@@ -0,0 +1,11 @@
+SDR
+
+### links
+https://github.com/jopohl/urh/
+https://www.windytan.com/
+
+### flipper zero
+https://gist.github.com/paucoma/57080d2845ba4b21b980b90842c38eb1
+https://gist.github.com/jinschoi/40a470e432c6ac244be8159145454b5c
+https://github.com/RogueMaster/flipperzero-firmware-wPlugins
+
diff --git a/linux_hardening.md b/linux_hardening.md
index 986990a..5b7d21d 100644
--- a/linux_hardening.md
+++ b/linux_hardening.md
@@ -29,6 +29,7 @@ http://jk.ozlabs.org/docs/sbkeysync-maintaing-uefi-key-databases/
 archlinux can build with AUR, debian/ubuntu can use the *.deb precompiled package. It should be available for x64, arm64 and arm
 
 ## data integrity aka bitrot
+ref: https://github.com/rfjakob/cshatag
 General kernel awareness:
 https://github.com/torvalds/linux/blob/master/Documentation/block/data-integrity.rst
 the solution so far to omit endusers hardware limitations (like ECC RAM *grml*)