Immarsat satellite phone

Two Chinese scientists have come up with a method of decrypting satellite phone communications, which works almost instantly and provides a third-party access to secure conversations in real-time.

Their method works against GMR-2, the latest version of the GEO-Mobile Radio Interface that is used to support communications from a satellite phone to overhead satellites.

GMR-2 encrypts all data sent from a user's phone to the satellite via a 64-bit key-length cipher.

New GMR-2 attack is much faster than previous one

In research papers published in 2012 and 2013, a team of five researchers from Ruhr University in Bochum, Germany, have developed a practical attack on the encryption of satellite phones that use the GMR-2 standard to secure communications.

While the German team's research turned heads at the time, the attack was complex, and hard to execute in real-world scenarios as it required time to pull of all the mathematical equations needed to recover the encryption key used to secure the satellite phone's communications.

In a research paper published last week, two Chinese researchers from the National University of Defense Technology in Changsha, China, have found a new attack on GMR-2 encryption that can be carried out in fractions of a second, allowing an attacker to get hold of the encryption key.

Chinese researchers reverse engineered GMR-2 encryption

The Chinese researchers say their method is different from the one devised by the German team. Instead of attempting to carry out "plaintext attacks" on the encryption key via methods such as "read-collision" and "guess-and-determine," the Chinese team reverse engineered the entire process of how the phone chooses an encryption key.

Their work allowed researchers to devise a system to determine the encryption key a satellite phone uses to encrypt its data just by looking at the already encrypted data sent from the phone.

While an academic and scientific success, this research can have catastrophic results in the real world, as this new attack could help with the creation of encryption-busting equipment that intercepts and breaks satellite phone communications.

Satellite phones are crucial equipment, often used in war zones, by intelligence agents, dissidents, and more.

Image credit: Immarsat