  Quantum key distribution (QKD) is a provably secure way for two distant
parties to establish a common secret key, which then can be used in a classical
cryptographic scheme. Using quantum entanglement, one can reduce the necessary
assumptions that the parties have to make about their devices, giving rise to
device-independent QKD (DIQKD). However, in all existing protocols to date the
parties need to have an initial (at least partially) random seed as a resource.
In this work, we show that this requirement can be dropped. Using recent
advances in the fields of randomness amplification and randomness expansion, we
demonstrate that it is sufficient for the message the parties want to
communicate to be (partially) unknown to the adversaries -- an assumption
without which any type of cryptography would be pointless to begin with. One
party can use her secret message to locally generate a secret sequence of bits,
which can then be openly used by herself and the other party in a DIQKD
protocol. Hence, our work reduces the requirements needed to perform secure
DIQKD and establish safe communication.
