To authenticate a battery pack, the host generates a 160-bit random challenge. The generated random challenge is transmitted to the authentication device, which uses the secret key along with the 160-bit random challenge from the host to calculate the authentication digest value.
The selection of the battery authentication scheme between the simple ID authentication and SHA-1/HMAC-based authentication depends on the security level needed and cost for the applications. The simple ID authentication is the least expensive and is good for cost-sensitive applications, but it is easy to replicate.
When the host and the authentication device have completed the calculation, the host reads the authentication digest value from the authentication device. It then compares it to its own value. If the values match, the battery pack is authenticated.
The presented battery authentication architectures meet the counterfeit battery challenges to protect OEM businesses and to promote end-user safety and satisfaction. Several authentication schemes currently are used to identify that a battery pack is intended for specific portable products. The most common is the form factor or physical connection.
To improve battery identification, an electrical identification scheme could be used so that simple physical counterfeiting is no longer enough to replicate the battery. Figure 1 shows the ID authentication functional block diagram. The challenger or host sends a command to read the data from the device (responder).
You would connect your DC 9V source to a plug identical to the one coming out of the adapter and plug that into the power jack on the tablet. A small 9V battery is not sufficient. Your best bet would be a lithium battery. It would run fine off 3 18650 cells in series and a 9V switching regulator.