There are mechanisms available to flash the recovery partition of an Android device with a modified image. The fastboot utility facilitates this process. Fastboot is a diagnostic protocol that comes with the SDK package and is used primarily to modify the flash filesystem through a USB connection from a host computer. For this, you need to start the device in boot loader mode, in which only the most basic hardware initialization is performed.

Once the protocol is enabled on the device, it will accept a specific set of commands that are sent to it via the USB cable using a command line. Flashing or rewriting a partition with a binary image stored on the computer is one such command that is allowed. Once the recovery is flashed, boot the device in recovery mode, mount the /data and /system partitions, and use adb to remove the gesture.key file. Reboot the phone and you should be able to bypass the screen lock; however, this works only if the device bootloader is unlocked. Also, flashing permanently alters the device. Instead of flashing, you could use the fastboot boot command to boot to a recovery image temporarily to delete the key file without permanently changing the recovery partition.