Secure communication network

A communication network for exchanging a combined cryptographic key between a first node and a second node,

• wherein the first node and the second node are connected through a first communication and a second communication network, the first communication network comprising a quantum communication network wherein information is encoded on weak light pulses, and comprising at least one intermediate node, other than the first node and the second node, said intermediate node configured to receive and transmit a signal encoded on weak light pulses, and
• the first node and the second node are configured to:
• exchange one or more first cryptographic keys on the first communication network;
• exchange one or more second cryptographic keys on the second communication network, wherein the second cryptographic key is exchanged between the first and second node with a quantum-resistant algorithm;
• and
• form the combined cryptographic key by combining the one or more first cryptographic keys and the one or more second cryptographic keys, such that the first node and the second node share knowledge of the combined cryptographic key,
• wherein the first node is configured to send information through the first communication network to:
• exchange a quantum cryptographic key with the at least one intermediate node;
• generate a local secret key, the local secret key being used to form the one or more first cryptographic keys;
• form a further key using the local secret key and the quantum cryptographic key;
• and
• transmit the further key to the at least one intermediate node.

A first node configured to exchange a combined cryptographic key with a second node on a communication network,

• the first node being connected to at least one intermediate node through a first communication network, the first communication network comprising a quantum communication network wherein information is encoded on weak light pulses, wherein the first communication network comprises at least one intermediate node, other than the first node and the second node, said intermediate node configured to receive and transmit a signal encoded on weak light pulses, wherein the first node is configured to exchange a quantum cryptographic key with the at least one intermediate node;
• the first node being directly connected to the second node using a second communication network;
• the first node and the second node being further configured to:
• exchange one or more first cryptographic keys on the first communication network;
• exchange one or more second cryptographic keys on the second communication network, wherein the second cryptographic key is exchanged between the first and second node with a quantum-resistant algorithm;
• and
• form the combined cryptographic key using the one or more first cryptographic keys and the one or more second cryptographic keys, such that the first node and the second node share knowledge of the combined cryptographic key
• wherein the first node is configured to send information through the first communication network to:
• exchange a quantum cryptographic key with the at least one intermediate node;
• generate a local secret key, the local secret key being used to form the one or more first cryptographic keys;
• form a further key using the local secret key and the quantum cryptographic key;
• and
• transmit the further key to the at least one intermediate node.