A group of security researchers detailed a real-time inversion attack against the GMR-2 stream cipher used in satellite phone communication, claiming it is much more efficient than previously devised attacks.
The research focused on the GMR-2 algorithm that is commonly used by modern-day satellite phones, including Inmarsat, to encrypt voice calls in an attempt to prevent eavesdropping.
The attack method helped researchers effectively reduce the search space for the 64-bit encryption key, which in turn made it easier to hunt for the decryption key, resulting in the encrypted data to be cracked within a fraction of a second.
The technique contains three phases, namely table generation; dynamic table looks-up, filtration and combination; and verification. The attack can be used to “retrieve the complete 8-byte encryption-key from only 1 frame (15 bytes) of keystream on average.” It also significantly reduces the exhaustive search space, and requires only 6KB of extra storage space.
The security researchers reveal that, in 10,000 experiments, the newly devised technique was able to uniquely determine 97.2% of the encryption-keys by the 15 bytes of keystream. The remaining 2.8% of the keys needed an extra keystream byte to retrieve.
No comments:
Post a Comment