ATSHA204 has low entropy on startup without seed update

[jbdatko]

The ATSHA204, not the ATSHA204A, has low entropy on device startup and will not produce random numbers without a seed update.

If you change this code and recompile the software, you will have poor random numbers. If you use the software as-is, which will update the seed on the device each time, you should be fine.

Atmel confirmed this behavior and the software, as implemented is using the manufacture recommend method.

This device works by using a seed -- if this bothers you, you are free to use a different random number generator. The major feature of this device is to securely store MAC keys anyway.

Regardless, for those who wish to use this device without a seed, there should be a warning message (with a user conformation) that allows them to use the device.

Alternatively, go get an ATSHA204A. This software will work with that device as well.