Are there any practical ways to transfer random data securely? The owner of the random.org service recommends that you do not use randomly generated numbers from their website in cryptographic keys. This makes sense, but it got me wondering. Is it possible to securely transfer random values in such a way that they are still viable for use in cryptography?  

They can be trivially transferred with a physical cable, but what about when such an instance is impossible? For instance, when a true random number generator is physically separated from the client which needs random numbers, and both machines are in control by the same person.  

Is this practical to do securely?
Is it possible to securely transfer random values in such a way that they are still viable for use in cryptography?


Yes and this is done all the time.

If you use a TLS_RSA cipher suite, the client uses RSA to encrypt key material, i.e. random values, and transfer that securely to the server for key derivation.


  The owner of the random.org service recommends that you do not use randomly generated numbers from their website for use in cryptographic keys.


The reason for this is not the security of transferring the random numbers (random.org is available through TLS), but the fact that you cannot be sure they are not storing or manipulating the numbers:


  We should probably note that while fetching the numbers via secure HTTP would protect them from being observed while in transit, anyone genuinely concerned with security should not trust anyone else (including RANDOM.ORG) to generate their cryptographic keys.


So it is possible, but you would have to trust the one generating and sending the random numbers.