regpg's threat model

decryption keys

Each person whose private key is listed in regpg's pubring.gpg is responsible for keeping their secret key safe from prying eyes, and safely backed up. It is a good idea to generate a new key specifically for use with regpg - see "revocation" below.

regpg requires the use of gpg-agent, which reduces the need to retype passphrases, which makes it more reasonable to have long random passphrases.

authority to decrypt

The contents of regpg's pubring.gpg determine who has access to secrets.

regpg is designed to be used with version control, so that changes to pubring.gpg are recorded and audited like any other code or configuration change.

With regpg, change reviews are important to protect against elevation of privilege by an attacker who gains write access to pubring.gpg. To make this easier, regpg init git installs a git diff hook for pubring.gpg.

existence of secrets

regpg does not try to hide secrets; we assume their existence is equally sensitive as any unencrypted code or configuration that shares the same repository.

backups

We assume that gpg encryption is strong enough that we can promiscuously distribute encrypted secrets via version control and backups, to keep them safe from accidental lossage.

If all the private decryption keys are lost then access to the secrets is lost. It is therefore vital to keep gpg private keys safe.

avoiding accidental exposure

We try to help regpg users maintain situational awareness of their secrets:

workstation compromise

regpg takes a couple of measures to reduce the consequences of a compromised workstation.

revocation

This is one of the weak points of regpg's setup. If you have access to the private part of a key previously included in pubring.gpg, and access to the repository, you can still decrypt secrets stored in old revisions.

Revoking access to regpg secrets requires destroying the private part of the key that was removed from pubring.gpg. Hence it is a good idea to use a regpg-specific key.

If you can't be sure that someone no longer has access to their private key after you revoked their access, you will have to replace all the secrets.

auditing

Another weak point. regpg supports distributed access to secrets. The only point of audit is access to revision control, but that does not tell anyone when secrets are decrypted.


Part of regpg https://dotat.at/prog/regpg/

Written by Tony Finch fanf2@cam.ac.uk dot@dotat.at
at Cambridge University Information Services.
You may do anything with this. It has no warranty.
https://creativecommons.org/publicdomain/zero/1.0/