SecKey 2.1.3 for Mac was available to download from the developer's website when we last checked. We cannot confirm if there is a free download of this app available. This free software for Mac OS X was originally designed by Lighthouse16. We recommend checking the downloaded files with any free antivirus. The application lies within Security Tools, more precisely Personal Security.
From the developer:
SecKey provides one time passwords to be used with the two factor authentication of Dropbox, Google, Facebook, GitHub, Proton Mail and many more. The tool adds a second layer of security for your online accounts. This works by generating one-time passwords on your mobile devices which can be used in conjunction with your normal password to make your login nearly impossible to hack.
You may want to check out more Mac applications, such as Password Repository, PassDirector or CiphSafe, which might be similar to SecKey.