Odin (firmware flashing software)
Odin is a utility software program developed and used by Samsung internally which is used to communicate with Samsung devices in Odin mode through the thor protocol. It can be used to flash a custom recovery firmware image to a Samsung Android device. Odin is also used for unbricking certain Android devices. Odin is the Samsung proprietary alternative to Fastboot.
There is no account of Samsung ever having officially openly released Odin, though it is mentioned in the developer documents for Samsung Knox SDK and some documents even instruct users to use Odin. Some other docs on Knox SDK reference "engineering firmware", which presumably can be a part of the Knox SDK along with Odin. Publicly available binaries are believed to be the result of leaks. The tool is not intended for end-users, but for Samsung's own personnel and approved repair centers.
Usage
Although none of the publicly available downloads are authorized by Samsung itself, XDA-Developers consider the files offered on their Forum the safest option. There is now a but it is not stable release.For the usage of Odin, the phone needs to be in Download mode. For this, some key combination need to be pressed, such as
Power + Volume Down + Home, or Power + Volume Down + Bixby, or connect to a computer while performing the Volume Up + Volume Down key combination.The thor protocol that Odin implements is used in many Samsung devices, including in some devices co-developed by Google and Samsung like the Galaxy Nexus. There is also an implementation of the thor protocol in Das U-Boot.