Instant Ciphertext-only Cryptanalysis of A5/2
Nan Jia · Communications technology · 2007
This paper presents a ciphertext-only cryptanalysis of A 5/2 ciphering algorithm in GSM encrypted communication. Since the error-correction code during the initialization of a conversation is conducted before the information encryption, the cryptanalysis makes use of the redundancy of the plaintext. Firstly, the cryptanalysis can be carried on without any plaintext, which makes the cryptanalysis very practical. Secondly, it is a real-time cryptanalysis. The cryptanalysis attack can find the correct key in less than a second after a 5.5 hours pre-computation.