For security personalization of a device within the production environment our customer requires the following:
The private / public key pair should be placed within the device and within the Secure process environment.
To generate the private key, parts of the entropy are to be generated by an external random number generator.
Corresponding random data should be imported into the device.
I understand what they want but have no idea, how this additional entropy could be combinded with the device internal true-random-number generator. I understand, that a number of external generated random numbers should be combinded with the internal generator to yield the random numbers on which my private keys shall be based. How is this done in practice? To take the first 16 numbers from the internal and the other 16 numbers from the external source would be by far too trivial.