The AirGap Vault is installed on a spare smartphone that has no connection to any network, thus it is air gapped. This app handles the private key.
airgap-vault-55947.apk: 8da2bd0573cbdc81bb4224a7e9df1821187239a45fd8b8362759d266110987a2 airgap-vault-knox-version-55948.apk: 444ae25e96aa807542e8f5761c40f03c72c9bd3c93ae73fd35b54cb1630d934e
airgap-vault-knox-version-55948.apk is a special version for AirGap Knox users to update their AirGap Vault app.