LTE-A空口监测仪NAS消息解密的研究与实现

RESEARCH AND IMPLEMENTATION OF NAS MESSAGE DECRYPTION IN LTE-A AIR INTERFACE MONITORING INSTRUMENT

随着LTE(Long Term Evolution)网络的成熟和商业化,运营商迫切需要测量仪器进行LTE网络状况分析。基于此进行LTE-A空口监测仪表的研发。LTE-Advance系统对非接入层NAS(Non-access stratum)部分消息进行了加密处理。以LTE安全层次和NAS加密/解密原理为基础,研究获取关键参数如KASME和加密算法类型的方法。通过编写C++程序实现参数的获取,并匹配相应算法函数完成解密。最后对Wireshark抓取的实际数据进行解密,完成程序有效性的验证,根据结果可以得出解密成功的结论。

With the maturity and commercialisation of LTE( Long-Term Evolution) networks,operators urgently need measuring instruments to analyse the network status in LTE networks. On this basis we carried out the research and development of LTE-A air interface monitoring instrument. The LTE-Advanced system makes encryption processing on part of messages in NAS( non-access stratum). Based on LTE security level and the encryption / decryption principle in NAS,we studied the approach for obtaining the key parameters such as KASME and the encryption algorithm types. By writing C + + program we implemented the acquisition of parameters,and matched the corresponding algorithm function to achieve the decryption. At last,we carried through the verification on the validity of the program by decrypting actual data fetched in Wireshark. According to the results,we could conclude that it is a successful decryption.