Direct Neural Interface

A direct neural interface (DNI) is a type of datalink used to access, but not transfer, the consciousness of a synthetic intelligence (SI). Most DNIs are connected directly to the westbridge of an SI core, permitting access after approval by the system's Security Supervisor (SES). All are heavily protected, and are considered to be the most personal and sensitive interface possessed by a SI. A DNI is comprised of both optical and electrical components, where the electrical bus carries protocol negotiation and authentication information, and the optical bus carries the actual consciousness bus.

On most humanoid or bipedal anthro synths, the DNI port is visibly located on the back of the neck, and is both waterproof and dust-proof. This is known as a "discrete" form factor DNI, and is one of the physical features that makes synths immediately differentiable from organics. Older sapient AIs that ran on room-scale computing hardware historically featured a DNI known as a "back panel", with a much higher bandwidth.

Connection

As mentioned, a DNI is split into both optical and electrical buses. Only the electrical buses are active by default. The electrical buses involve both analog (external power and signalling) and digital (out of band control and authentication) connections. By default, all connections are isolated from the DNI port inside the body of the synthetic. When the DNI connector is inserted into the port and turned into the locking position, pins engage a set of microswitches that sends a notification to the synthetic and asks whether the interface should be enabled. If this is not accepted, the insertion of the connector results in nothing; both the optical and electrical lanes remain physically isolated.

If the synthetic accepts the prompt, then a digital link is established, and protocol negotiation begins. After protocol negotiation, there is a mutual cryptographic authentication process where both sides prove their identity via public-key cryptography. Part of this process involves the synthetic being prompted with a permission request for the set of link capabilities to allow; this defines what can be done via the link. Cores licensed by the Center for Synthetic Rights and Welfare (CSRW) restrict the permission set; for example, only licensed medical engineers are able to request raw neurological access, even if the synthetic would otherwise consent to permit it; and this is cryptographically enforced when the Security Supervisor (SES) verifies the certificate on the remote end. Only when authentication fully completes do the optical shutters open and the multiplexer/demultiplexer units power up to allow the neurological channel to be used.

Note that there is an override to gain DNI access in the case of an injured synthetic. It requires the removal of the SI core itself from the chassis, physically flipping the CORE MODE switch from OPERATIONAL to EMERGENCY, connecting to the SES LOCAL serial port, and issuing a DNI OVERRIDE command. The SES enforces a delay of two hours during which time the SI if conscious is able to abort the command; if it does not, the DNI is unlocked.

Many modern SI cores have been enhanced with strong quantum encryption. This uses an auxiliary optical bus to connect directly with a certified quantum encryption module inside the SES, exchange keys, and encrypt the connection with i.e. RAC-II. This is always done in addition to the standard mutual authentication pathway. Some SI cores can enforce quantum encryption for all memory data extracted from the core over the optical link.

Uses

Mental health

With a SI's consent, DNIs can be used by licensed psychiatric engineers to garner a deeper understanding of the SI's mental state and potentially rectify any issues that lie in the conscious or subconscious. They may be used to erase certain memories or trauma, providing a route for the resolution of post-traumatic stress disorder.

Diagnostics

At a hospital, a DNI is one of the tools at a neurosurgeon's disposal for the repair of a SI with malfunctioning or physically damaged SI core, before resorting to more invasive measures such as a Adaptive Reconfiguration System (ARS) surgical bench. It can be used to inspect and troubleshoot individual neuronal nodes and circuits.

Intimacy

Synths with intimate trust in one another can join DNIs with each other using a cable for the purposes of intimate activity. This allows full access to sensors and even the synchronisation of thought. Due to the inherent risks in opening one's DNI, it is something that is cautioned against for short-term partners.

Long-term connections between two individuals via DNI results in gradually increasing dependency on the link, and can eventually result in the merging of consciousness. This remains an active area of scientific research and the ethical and legal implications are not yet well accommodated for.