`sudo apt-key adv` not working (company proxy?)

I am working with Ubuntu 16.04.5 LTS.

If I run sudo apt-get update in the terminal, I get:

W: GPG error: https://repo.pbis.beyondtrust.com/apt pbiso InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY FDE053D27237D0AC W: The repository 'https://repo.pbis.beyondtrust.com/apt pbiso InRelease' is not signed. N: Data from such a repository can't be authenticated and is therefore potentially dangerous to use. N: See apt-secure(8) manpage for repository creation and user configuration details. 

So I then try running sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys FDE053D27237D0AC, and the command just sits there for a few minutes until it fails with the message:

gpg: requesting key 7237D0AC from hkp server keyserver.ubuntu.com gpg: keyserver timed out gpg: keyserver receive failed: keyserver error 

I have already gone into /etc/apt/apt.conf and added the lines

Acquire::http::proxy "<my company's proxy>"; Acquire::https::proxy "<my company's proxy>"; 

Add a PPA with key completely manually, without `add-apt-repository` OR `apt-key adv –recv-keys`

I need the exact and complete series of shell incantations for adding a PPA with key in the following situation:

  • add-apt-repository is not installed
  • gnupg and gnupg2 are not installed, making it impossible to use apt-key adv --recv-keys
  • installing those missing tools beforehand is to be avoided at all cost because in the context of docker image building it would require another apt-get update run which is slooooowwwwwwww