I have installed android sdk in my Windows machine.
Under user path / .android folder there are two files: adbkey and adbkey.pub
What is use of these two files and what information does it contains.
I use different vendor android devices for adb operation. How does it relate to this.
1 Answer
It's an authentication key, similar to e.g. TLS client certificates or SSH user keypairs. The adb client uses it to prove to the Android device that it is still the same "trusted" computer as before.
Because of USB becoming the primary charging port as well as the debugging port, it now has the same security risks as network access, and the Android device needs to prevent untrusted systems (e.g. malicious chargers) from accessing your data through the adb interface. So whenever you connect from a computer using adb, the phone recognizes it based on the adbkey file and either accepts the connection or shows a prompt saying "it's a new computer, do you want to trust it".
