Preventing wiretapping by using a dedicated terminal, ‘Bi-Hwa-Gi’ for secret communication
KT-EYL, Development of Technology to Implement Non-Speech Communications with General Terminals
Combining a quantum random number generator and a quantum key distribution system


Secret communication is a communication method that prevents wiretapping by using a dedicated terminal called a secret phone. When voice data from a communication terminal is encrypted and transmitted, the recipient receives the data as the original sound. It is mainly used in the defense sector and national intelligence agencies where security is important.

On the 10th, KT developed a technology that can implement quantum cryptography secret communication without using a dedicated terminal. If this technology is applied, secret communication is possible with a general smartphone, so even private companies can easily build a quantum cryptography secret communication system.

The core of quantum cryptography communication technology is the 'quantum secure communication terminal' that encrypts voice calls when connected to a smartphone. When a quantum secure communication terminal is connected to the sender and receiver's smartphones during a secret communication, the security mode is activated and the call content is encrypted. Encrypted call content is decrypted using a ‘quantum encryption key’ synchronized in secure mode.

KT has strengthened security by combining a technology that combines a ‘Quantum Random Number Generator (QRNG)’ and a ‘Quantum Key Distributor (QKD)’. QRNG generates a quantum random number array without specific rules or algorithms. QKD generates a quantum encryption key from this array and transmits it to a quantum secure communication terminal.

Previously, encryption was done using only QRNG, but with the additional application of QKD, the level of information security has been significantly improved. In addition, decryption is impossible without a quantum cryptographic key.

Based on this technology development, private companies other than existing organizations using secret communication can also use secret communication to prevent confidentiality leaks. For example, it can maintain confidentiality of conversations between lawyers and clients in legal proceedings. In addition, it can reduce the possibility of corporate secrets being leaked in spaces outside the office when working remotely.

KT jointly developed this quantum cryptography communication technology that follows ITU-T international standards with domestic security startup EYL. EYL possesses the original technology for developing an ultra-small quantum cryptography chip that was selected as a key technology for the U.S. Air Force security system.

Meanwhile, a quantum cryptography communication security network was built in the Jeonnam Provincial Office and the Navy's 3rd Fleet Command in January of this year. This is the result of the 'Quantum Cryptography Communication Pilot Infrastructure Construction and Operation' project conducted for four months from September of last year with the Ministry of Science and ICT and the National Intelligence Service (NIA) in accordance with the government's 'Digital New Deal' plan.