How to generate gpg signing keys in bintray for jcenter in windows

For Linux/Mac you can use gpg. I learned how to do this here. I needed to prefix the following commands with sudo.

1. Generate the keys

   gpg --gen-key
   

   Follow the defaults but enter your name and email and optionally a password.

2. List the keys.

   gpg --list-keys
   

   which should show something like this:

   pub   2038R/91E83BF2 2017-05-13
   uid                  Bob <[email protected]>
   sub   2038R/E3872671 2017-05-13
   

3. Upload the public key to a keyserver

   gpg --keyserver hkp://pool.sks-keyservers.net --send-keys PUBLIC_KEY_ID
   

   replacing PUBLIC_KEY_ID with your id (91E83BF2 in the example above).

4. Export your public and private keys to a text file

   gpg -a --export [email protected] > public_key_sender.asc
   gpg -a --export-secret-key [email protected] > private_key_sender.asc
   

5. Copy the contents of these files to Bintray at Edit Profile > GPG signing.

Windows users can generate GPG keys using GPG4Win.
There are many tutorials available, for example this one.