System access using a mobile device

A mobile device, comprising:

• one or more processing elements configured to:
• receive, from a sharing device, information indicating an action to be authorized for the mobile device, wherein the action is associated with another system;
• transmit, to the sharing device, a certificate that is signed and embeds the action and a public key of the mobile device;
• receive, from the sharing device based on verification of the public key and the certificate, a signed version of the certificate that was signed to produce an additional signature using a private key of the sharing device that was established during a pairing session between the sharing device and the other system;
• transmit the signed certificate to the other system for inclusion of the mobile device as an authorized device for the action based on validation of the additional signature and validation of the certificate;
• and
• request the action from the other system.

A system, comprising:

• one or more processing elements configured to:
• receive, from a sharee device, a signed certificate, wherein the certificate embeds an action authorized by a sharing device for the sharee device, wherein the certificate is generated by the sharee device and signed by the sharing device to produce a signature using a private key of the sharing device that was established during a pairing session between the sharing device and the system;
• validate the signature of the sharing device and certificate;
• store information indicating the sharee device as an authorized device for the action;
• and
• initiate the action, in response to a request to perform the action from the sharee device.