Uploaded December 2019 | Updated September 2026, 1 day ago
The presentation demonstrates that the security of the A5/1 and A5/3 ciphers used to protect cellular calls are vulnerable to compromise leading to full decryption of GSM communications, using freely available open source solutions along with our tools we developed for this task.
The flaw being exploited lies in the heart of the design of GSM. In all implementations the standard requires GSM messages to first be error control encoded using a convolutional code and then encrypted. In the vast majority of implementations used today, encryption is performed using the A5/1 or A5/3 cipher. The convolutional code adds redundancy to the transmitted message, which can act like a fingerprint to identify the key used to encrypt the GSM message.
To exploit the vulnerability an attacker simply needs to capture a transmission and identify the GSM channel used. The standard defines the convolutional code and therefore how the redundancy may be interpreted to recover the encryption key.
This presentation considers passively capturing GSM traffic using A5/3 encryption and demonstrates a novel solution to cracking the key used without interacting with the mobile or network.
The presentation demonstrates that the security of the A5/1 and A5/3 ciphers used to protect cellular calls are vulnerable to compromise leading to full decryption of GSM communications, using freely available open source solutions along with our tools we developed for this task.
The flaw being exploited lies in the heart of the design of GSM. In all implementations the standard requires GSM messages to first be error control encoded using a convolutional code and then encrypted. In the vast majority of implementations used today, encryption is performed using the A5/1 or A5/3 cipher. The convolutional code adds redundancy to the transmitted message, which can act like a fingerprint to identify the key used to encrypt the GSM message.
To exploit the vulnerability an attacker simply needs to capture a transmission and identify the GSM channel used. The standard defines the convolutional code and therefore how the redundancy may be interpreted to recover the encryption key.
This presentation considers passively capturing GSM traffic using A5/3 encryption and demonstrates a novel solution to cracking the key used without interacting with the mobile or network.
![Black Hat USA 2018 - Mainframe [z/OS] Reverse Engineering and Exploit Development](https://i.ytimg.com/vi/opBLBYAR8tU/mqdefault.jpg "Black Hat USA 2018 - Mainframe [z/OS] Reverse Engineering and Exploit Development
Speak with any Fortune 500 running mainframe and theyll tell you two things: (1) without their mainframes theyd be out of business (2) they do not conduct any security research on them, let alone vulnerability scans. The most infuriating part is that mainframes are simply computers, theyre different from what youre used to, but that doesnt mean they cant be hacked. Previous talks about this topic have covered the platform from a high level, imploring you to do the basics. This talk continues this series of talks, given by others, around mainframe hacking. Previously covered topics included network penetration testing and privilege escalation. To complement those talks, this talk will expose attendees to the various tools that exist on the platform to help you do your own reverse engineering, followed by detailed steps on how to start your own exploit development. Attendees will learn what debuggers are available on the platform, such as dbx and ASMIDF, as well as the challenges youll have using them. After learning how to RE, attendees will then learn how to develop their own exploits and buffer overflows on the platform using C, assembler and JCL. A demo program will be used to teach all these items so people can follow along. Topics included in this discussion are APF authorization, bypassing RACF/ACEE, TSO, Unix System Services.")
