DCK pinning attack in TETRA

A weakness in TETRA's authentication lets an attacker who can predict a specific challenge value intercept communications and force the session key to zero, making encrypted conversations readable.

The vulnerability exploits predictability of the MS challenge RAND2 in TETRA's authentication procedure, allowing a man-in-the-middle adversary to manipulate the Derived Cipher Key (DCK) negotiation to a null state, thereby compromising session encryption without detection.