paperkey: add page (#6378)

pages/common/paperkey.md

@@ -0,0 +1,16 @@
+# paperkey
+
+> An OpenPGP key archiver.
+> More information: <https://www.jabberwocky.com/software/paperkey/>.
+
+- Take a specific secret key and generate a text file with the secret data:
+
+`paperkey --secret-key {{path/to/secret_key.gpg}} --output {{path/to/secret_data.txt}}`
+
+- Take the secret key data in `secret_data.txt` and combine it with the public key to reconstruct the secret key:
+
+`paperkey --pubring {{path/to/public_key.gpg}} --secrets {{path/to/secret_data.txt}} --output {{secret_key.gpg}}`
+
+- Export a specific secret key and generate a text file with the secret data:
+
+`gpg --export-secret-key {{key}} | paperkey --output {{path/to/secret_data.txt}}`