The new Google Developer Console provides two kind of private keys.
the first one is a json file which contains all the information that is necessary to authenticate with a service account. this file gets downloaded when you create a new service account in the Google Developer Console.
it's structure is as follows:
the second type of private key is a .p12 file. it can be also downloaded in the Google Developer Console. this file is a PKCS12 keystore and contains a private key that can be used to authenticate a service account. the keystore password and key password is "notasecret". the key alias is "privatekey".
it would be nice to let the user choose between this two options when creating google oauth credentials in jenkins.