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Karsten Nohl (born 11 August 1981) [1] is a German cryptography expert [2] and hacker. His areas of research include Global System for Mobile Communications (GSM) security, radio-frequency identification (RFID) security, and privacy protection. [3]
Nohl grew up in the Rhineland area of Germany and studied electrical engineering at the SRH University Heidelberg from 2001 to 2004. [1] [3] From 2005 to 2008, he earned his PhD at the University of Virginia on Implementable Privacy for RFID Systems. [3] Since 2010 Nohl has served as the Managing Director and Chief Scientist of the Berlin-based consultancy and think tank, Security Research Labs. [3] [4] [5] Karsten has also served as interim CISO for the Indian corporation Jio from 2014 to 2017, as well as, for the Malaysian corporation Axiata in 2017. [4]
Together with Henryk Plötz and CCC Berlin's, Starbug, Nohl gave a presentation in December 2007 on how the encryption algorithm used in Mifare Classic RFID smart cards was cracked. The Mifare Classic Card has been used in many micropayment applications, such as the Oyster card, CharlieCard, or the OV Chipkaart for payment. [6] [7] [8]
Together with Henryk Plötz, Nohl gave a presentation in December 2009 documenting the flawed security of Legic Prime RFID security. The talk demonstrated how the system employed multiple layers of strange and obscure techniques in lieu of standard encryption and cryptographic protocols. This allowed cards to be read, emulated, and even for arbitrary master tokens to be created. [9]
At SIGINT-2013, Nohl gave a presentation on the insecurity of electronic car immobilizers used to prevent vehicle theft, documenting vulnerabilities in the three most widely used systems: DST40 (Texas Instruments), Hitag 2 (NXP Semiconductors) and Megamos (EM Micro). [10]
Nohl was part of the project group deDECTed.org [11] [11], which in 2008 at 25C3 pointed out serious deficiencies in the DECT protocol. [12]
In April 2010, Nohl, together with Erik Tews and Ralf-Philipp Weinmann, published details on the cryptographic analysis of DECT proprietary and secret encryption algorithm used (DECT standard cipher), which is based on reverse engineering of DECT hardware and descriptions from a patent specification. [13]
In the summer of 2009 Nohl introduced the A5/1 Security Project. [14] The project demonstrated an attack on the GSM encryption standard A5/1 using Rainbow Tables. With the help of volunteers, the key tables were calculated in a few months and published on the 26C3 in December 2009. [15]
The GSM Association described Nohl's plans as illegal and denied that wiretapping was actually possible. He replied that his research was purely academic. [16]
As early as 2008, the hacker group THC had begun with the pre-calculation of key tables for A5 / 1, but probably never published the tables because of legal problems. [14]
At the 27C3 in December 2010, Nohl, together with Sylvain Munaut, demonstrated how mobile calls can be cut and decrypted with the help of converted cheap mobile phones and the open-source software OsmocomBB. [17] The pair showed that the GSM encryption can be cracked "in about 20 seconds" and that calls can be recorded and played back. [18] [19]
At Chaos Communication Camp 2011, Nohl and Luca Melette gave a presentation showing how GPRS networks do not securely encrypt their mobile traffic. [20] The pair stated that they had recorded data transmissions in the networks of several German mobile providers, including Deutsche Telekom, O2 Germany, Vodafone and E-Plus. [2] Several mobile service providers used either no or only insufficient encryption. With a modified mobile phone, mobile traffic could be read from within a radius of five kilometers. [2]
At both Black Hat 2013 and OHM 2013, Nohl demonstrated that many SIM cards use the outdated and insecure DES encryption, undermining the privacy and security of mobile phone users. [21] [22] [23] Through "Over The Air (OTA)" communication, such as SMS messages, it is possible to provide a SIM card with updates, applications, or new encryption keys. Such messages are digitally signed with DES, 3DES or AES. [22] [23] Nohl generated a Rainbow Table for 56-bit DES within a year based a on specially signed error message with known plain text. [22] [23] The resulting attack scenario: an attacker sends the victim a signed text message. [22] [23] With the help of the Rainbow Table it is then possible to crack the DES key of a SIM card in minutes and crack the internal key. (Known Plaintext Attack). [21] [22] This allows an attacker to send a signed SMS, which in turn loads a Java app onto the SIM card. These apps are capable of multiple actions, including sending SMS or sharing the location of the device. An attacker could, for example, command a device to send SMS messages to foreign premium services at the cost of the device owner. [22] [23] In principle, the Java Virtual Machine should make sure that every Java app can only access predefined interfaces. [23] Nohl found that the Java sandbox implementations of at least two major SIM card manufacturers, including market leader Gemalto, are insecure and it is possible for a Java app to escape the sandbox environment and thus gain access to the entire SIM card. [23] This makes it possible to duplicate SIM cards including the IMSI, authentication key (Ki) and payment information stored on the card. [23]
At the 30C3 in December 2013, Nohl introduced the Android app "GSMmap". Initially designed for use on a Galaxy S2 or S3 (including root access), the app collects information on the level a mobile network secures its traffic. The collected data can be uploaded, with the app user’s consent, to a database that evaluates the security of mobile networks worldwide, based on selected protection capability criteria. The results of this analysis are displayed on the "GSM Security Map" website, where the security level of mobile providers are visualized on an interactive world map and made available for download as "country reports".
At the 31C3 in December 2014, Nohl presented the Android app "SnoopSnitch" as a possible countermeasure against various mobile network security attacks. On various smartphones models with Qualcomm chipset and root access, mobile network traffic can be collected and analyzed locally with "SnoopSnitch,” where the app gives the user information about the encryption and authentication algorithm being used by the network, the possibility for SMS and SS7 attacks, as well as the potential presence of IMSI-catchers.
The data collected via “SnoopSnitch” can also be uploaded, with the user’s consent, to a database to support additional security analysis, which is shared on the "GSM Security Map" website.
Also at the 31C3, Nohl presented a side channel attack using Signaling System 7 (SS7) on UMTS communication and described other SS7-based attacks that can allow the reading of text messages, the determination of location coordinates, and various scenarios for fraud.
In April 2018, Nohl presented on security in the mobile Android environment. [24] Nohl and his colleagues analyzed Android firmware images from various smartphone vendors. In some cases, a so-called "patch gap" was found, where vendors had not applied all security patches that otherwise should have been present based on the monthly patch level date specified in the firmware. Nohl released an updated version of the open source “Snoopsnitch” app with new features to allow users to run tests on their Android phones to check for a "patch gap" on their device. [25]
At the 32C3, Nohl and colleagues presented an attack on the EC card protocols ZVT and Poseidon, which are a dialect of ISO 8583. [26] [27] Both protocols are the most common payment protocols in German-speaking countries.
At the 33C3, Nohl and colleagues highlighted security holes in Amadeus, Sabre, and Travelport, three of the largest Global Distribution Systems (GDS) which combined, handle approximately 90% of worldwide flight reservations and a large proportion of hotel, car rental, and other travel bookings. [28]
At Black Hat 2014, Nohl and Jacob Lell presented on security risks associated with USB devices. [29] [30] [31] [32] The USB standard is versatile and includes many different classes of devices. [31] Their research is based on the reprogramming of USB controller chips, which are widely used and found in USB sticks. [31] There is no effective protection against reprogramming, so a harmless USB device can be converted and used as a malicious device in many ways. [31]
Possible scenarios for abuse include:
Preventing such attacks is not yet possible because malware scanners have no access to the firmware version of USB devices and behavior detection is difficult. [31] USB firewalls that can block only certain device classes do not (yet) exist. [31] The usual process to remove malware - reinstalling the operating system - fails here because the USB stick that installs the operating systems may itself already be infected, as well as a built-in webcam or other USB devices. [31]
In addition, a proof of concept for Android devices was released to test the security. [31]
The Global System for Mobile Communications (GSM) is a standard developed by the European Telecommunications Standards Institute (ETSI) to describe the protocols for second-generation (2G) digital cellular networks used by mobile devices such as mobile phones and tablets. GSM is also a trade mark owned by the GSM Association. "GSM" may also refer to the voice codec initially used in GSM.
Short Message Service, commonly abbreviated as SMS, is a text messaging service component of most telephone, Internet and mobile device systems. It uses standardized communication protocols that let mobile phones exchange short text messages, typically transmitted over cellular networks.
Signalling System No. 7 (SS7) is a set of telephony signaling protocols developed in the 1970s that is used to set up and tear down telephone calls on most parts of the global public switched telephone network (PSTN). The protocol also performs number translation, local number portability, prepaid billing, Short Message Service (SMS), and other services.
A SIMcard is an integrated circuit (IC) intended to securely store an international mobile subscriber identity (IMSI) number and its related key, which are used to identify and authenticate subscribers on mobile telephone devices. SIMs are also able to store address book contacts information, and may be protected using a PIN code to prevent unauthorized use.
A5/1 is a stream cipher used to provide over-the-air communication privacy in the GSM cellular telephone standard. It is one of several implementations of the A5 security protocol. It was initially kept secret, but became public knowledge through leaks and reverse engineering. A number of serious weaknesses in the cipher have been identified.
Network switching subsystem (NSS) is the component of a GSM system that carries out call out and mobility management functions for mobile phones roaming on the network of base stations. It is owned and deployed by mobile phone operators and allows mobile devices to communicate with each other and telephones in the wider public switched telephone network (PSTN). The architecture contains specific features and functions which are needed because the phones are not fixed in one location.
An over-the-air update, also known as over-the-air programming, is an update to an embedded system that is delivered through a wireless network, such as Wi-Fi or a cellular network. These embedded systems include mobile phones, tablets, set-top boxes, cars and telecommunications equipment. OTA updates for cars and internet of things devices can also be called firmware over-the-air (FOTA). Various components may be updated OTA, including the device's operating system, applications, configuration settings, or parameters like encryption keys.
MIFARE is a series of integrated circuit (IC) chips used in contactless smart cards and proximity cards.
A one-time password (OTP), also known as a one-time PIN, one-time passcode, one-time authorization code (OTAC) or dynamic password, is a password that is valid for only one login session or transaction, on a computer system or other digital device. OTPs avoid several shortcomings that are associated with traditional (static) password-based authentication; a number of implementations also incorporate two-factor authentication by ensuring that the one-time password requires access to something a person has as well as something a person knows.
An international mobile subscriber identity-catcher, or IMSI-catcher, is a telephone eavesdropping device used for intercepting mobile phone traffic and tracking location data of mobile phone users. Essentially a "fake" mobile tower acting between the target mobile phone and the service provider's real towers, it is considered a man-in-the-middle (MITM) attack. The 3G wireless standard offers some risk mitigation due to mutual authentication required from both the handset and the network. However, sophisticated attacks may be able to downgrade 3G and LTE to non-LTE network services which do not require mutual authentication.
The HTC Universal is a Windows Mobile 5.0 Pocket PC PDA manufactured by High Tech Computer Corporation. It was the first 3G/UMTS-enabled Pocket PC PDA with a telecommunications function, and also the first to come with Windows Mobile 5.0 pre-installed.
SIM Application Toolkit (STK) is a standard of the GSM system which enables the subscriber identity module to initiate actions which can be used for various value-added services. Similar standards exist for other network and card systems, with the USIM Application Toolkit (USAT) for USIMs used by newer-generation networks being an example. A more general name for this class of Java Card-based applications running on UICC cards is the Card Application Toolkit (CAT).
Crypto1 is a proprietary encryption algorithm and authentication protocol created by NXP Semiconductors for its MIFARE Classic RFID contactless smart cards launched in 1994. Such cards have been used in many notable systems, including Oyster card, CharlieCard and OV-chipkaart.
Massachusetts Bay Transportation Authority v. Anderson, et al., Civil Action No. 08-11364, was a challenge brought by the Massachusetts Bay Transportation Authority (MBTA) to prevent three Massachusetts Institute of Technology (MIT) students from publicly presenting a security vulnerability they discovered in the MBTA's CharlieCard automated fare collection system. The case concerns the extent to which the disclosure of a computer security flaw is a form of free speech protected by the First Amendment to the United States Constitution.
Private GSM solutions appeared after the deregulation of the DECT guard band in some countries, allowing users and businesses to reduce their costs without impacting their performance, and to offer a number of value-added services. These benefits arose from the ability to create private mobile GSM networks, enabling mobile phone users to access the same services and features as users of a PBX extension.
Multi-factor authentication is an electronic authentication method in which a user is granted access to a website or application only after successfully presenting two or more pieces of evidence to an authentication mechanism. MFA protects personal data—which may include personal identification or financial assets—from being accessed by an unauthorized third party that may have been able to discover, for example, a single password.
Phone hacking is the practice of exploring a mobile device, often using computer exploits to analyze everything from the lowest memory and CPU levels up to the highest file system and process levels. Modern open source tooling has become fairly sophisticated to be able to "hook" into individual functions within any running app on an unlocked device and allow deep inspection and modification of its functions.
Mobile security, or mobile device security, is the protection of smartphones, tablets, and laptops from threats associated with wireless computing. It has become increasingly important in mobile computing. The security of personal and business information now stored on smartphones is of particular concern.
The Nokia Asha 310, also known as the Nokia Asha 310 or the Nokia ASHA 310 RM-911, was released in March 2013. It is the first in the line of the Asha range of phones to have dual subscriber identity module (SIM) slots and Wi-Fi connectivity. It was a reinvention of the Asha range to remain competitive with new Android devices. It cost $102.00 at its launch date. It has a touchscreen, comes with either a 2 or 4 GB micro SD card, and has 64 MB of RAM, a 2.0 MP camera and a battery that can last up to 600 hours in standby mode. The phone can play music for up to 54 hours or video for up to 9.5 hours, and has a maximum of 17 hours talk time (2G).
Osmocom is an open-source software project that implements multiple mobile communication standards, including GSM, DECT, TETRA and others.
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