Roel Verdult

Dismantling MIFARE Classic

The mifare Classic is a contactless smart card that is used extensively in access control for office buildings, payment systems for public transport, and other applications. We reverse engineered the security mechanisms of this chip: the authentication protocol, the symmetric cipher, and the initialization mechanism. We describe several security vulnerabilities in these mechanisms and exploit these vulnerabilities with two attacks; both are capable of retrieving the secret key from a genuine reader. The most serious one recovers the secret key from just one or two authentication attempts with a genuine reader in less than a second on ordinary hardware and without any pre-computation. Using the same methods, an attacker can also eavesdrop the communication between a tag and a reader, and decrypt the whole trace, even if it involves multiple authentications. This enables an attacker to clone a card or to restore a real card to a previous state.

Wirelessly Pickpocketing a Mifare Classic Card

The Mifare Classic is the most widely used contactless smartcard on the market.The stream cipher CRYPTO1 used by the Classic has recently been reverse engineered and serious attacks have been proposed. The most serious of them retrieves a secret key in under a second. In order to clone a card, previously proposed attacks require that the adversary either has access to an eavesdropped communication session or executes a message-by-message man-in-the-middle attack between the victim and a legitimate reader. Although this is already disastrous from a cryptographic point of view, system integrators maintain that these attacks cannot be performed undetected.This paper proposes four attacks that can be executed by an adversary having only wireless access to just a card (and not to a legitimate reader). The most serious of them recovers a secret key in less than a second on ordinary hardware. Besides the cryptographic weaknesses, we exploit other weaknesses in the protocol stack. A vulnerability in the computation of parity bits allows an adversary to establish a side channel. Another vulnerability regarding nested authentications provides enough plaintext for a speedy known-plaintext attack.

Practical Attacks on NFC Enabled Cell Phones

Near Field Communication (NFC) technology enables devices to communicate wirelessly within proximity distance. These NFC devices are often embedded into smart posters that offer the ability to exchange small files, photos and contact details. The Nokia 6212 Classic is currently the most popular NFC phone. It allows users to easily exchange digital objects using the NFC interface. To do so, two phones should be within the proximity coupling distance of 5 cm. This paper shows that the NFC feature that invokes a Bluetooth connection without user consent can be abused to surreptitiously install malicious software on the phone. This results in a serious vulnerability when smart posters start installing malicious software or spreading viruses.

Dismantling SecureMemory, CryptoMemory and CryptoRF

The Atmel chip families SecureMemory, CryptoMemory, and CryptoRF use a proprietary stream cipher to guarantee authenticity, confidentiality, and integrity. This paper describes the cipher in detail and points out several weaknesses. One is the fact that the three components of the cipher operate largely independently; another is that the intermediate output generated by two of those components is strongly correlated with the generated keystream. For SecureMemory, a single eavesdropped trace is enough to recover the secret key with probability 0.57 in 2^{39} cipher ticks. This is a factor of 2^{31.5} faster than a brute force attack. On a 2 GHz laptop, this takes around 10 minutes. With more traces, the secret key can be recovered with virtual certainty without significant additional cost in time. For CryptoMemory and CryptoRF, if one has 2640 traces it is possible to recover the key in 2^{52} cipher ticks, which is 2^{19} times faster than brute force. On a 50 machine cluster of 2 GHz quad-core machines this would take less than 2 days.

Using NFC phones for proving credentials

In this paper we propose a new solution for mobile payments called Tap2 technology. To use it, users need only their NFC-enabled mobile phones and credentials implemented on their smart cards. An NFC device acts like a bridge between service providers and secure elements and the secure credentials (on the card) are never revealed. In this way, secure authentication can be obtained by means of anonymous credentials, implemented on a smart card to provide the functionality with minimal data disclosure. We propose to use zero-knowledge proofs based on attribute-based anonymous credentials to provide the security and privacy requirements in mobile payments. Other use cases include online shopping, easy payment, eGoverment proofs etc.

Dismantling iClass and iClass Elite

With more than 300 million cards sold, HID iClass is one of the most popular contactless smart cards on the market. It is widely used for access control, secure login and payment systems. The card uses 64-bit keys to provide authenticity and integrity. The cipher and key diversification algorithms are proprietary and little information about them is publicly available. In this paper we have reverse engineered all security mechanisms in the card including cipher, authentication protocol and key diversification algorithms, which we publish in full detail. Furthermore, we have found six critical weaknesses that we exploit in two attacks, one against iClass Standard and one against iClass Elite (a.k.a., iClass High Security). In order to recover a secret card key, the first attack requires one authentication attempt with a legitimate reader and 222 queries to a card. This attack has a computational complexity of 240 MAC computations. The whole attack can be executed within a day on ordinary hardware. Remarkably, the second attack which is against iClass Elite is significantly faster. It directly recovers the master key from only 15 authentication attempts with a legitimate reader. The computational complexity of this attack is lower than 225 MAC computations, which means that it can be fully executed within 5 seconds on an ordinary laptop.

A Toolbox for RFID Protocol Analysis

Many RFID tags and contact less smart cards use proprietary security mechanisms for authentication and confidentiality. There are several examples in the literature showing that once these mechanisms have been reverse engineered, their security turns out to be unsatisfactory. Since the use of these tags is quickly expanding to access control and ticketing systems, it is important to independently assess their security. In this paper, we propose three tools for the analysis of RFID protocols. These tools facilitate message eavesdropping and emulation of both tags and readers. The tools focus on high frequency tags but one of them also supports low frequency. These tools are fully programable and allow for quick prototyping, testing and debugging of new RFID protocols. All the software, firmware and hardware we have developed that is described here is open source and open design.

PIE: Parser Identification in Embedded Systems

Embedded systems are responsible for the security and safety of modern societies, controlling the correct operation of cars and airplanes, satellites and medical equipment, military units and all critical infrastructures. Being integrated in large and complex environments, embedded systems need to support several communication protocols to interact with other devices or with their users. Interestingly, embedded software often implements protocols that deviate from their original specifications. Some are extended with additional features, while others are completely undocumented. Furthermore, embedded parsers often consist of complex C code which is optimized to improve performance and reduce size. However, this code is rarely designed with security in mind, and often lacks proper input validation, making those devices vulnerable to memory corruption attacks. Furthermore, most embedded designs are closed source and third party security evaluations are only possible by looking at the binary firmware. In this paper we propose a methodology to identify parsers and complex processing logic present in binary code without access to their source code or documentation. Specifically we establish and evaluate a heuristic for detecting this type of code by means of static analysis. Afterwards we demonstrate the utility of this heuristic to identify firmware components treating input, perform reverse engineering to extract protocols, and discover and analyze bugs on four widely used devices: a GPS receiver, a power meter, a hard disk drive (HDD) and a Programmable Logic Controller (PLC).

Prevent Session Hijacking by Binding the Session to the Cryptographic Network Credentials

Many cyber-physical applications are responsible for safety critical or business critical infrastructure. Such applications are often controlled through a web interface. They manage sensitive databases, drive important SCADA systems or represent imperative business processes. A vast majority of such web applications are well-known to be vulnerable to a number of exploits. The focus of this paper is on the vulnerability of session stealing, also called session hijacking. We developed a novel method to prevent session stealing in general. The key idea of the method is binding the securely negotiated communication channel to the application user authentication. For this we introduce a server side reverse proxy which runs independently from the client and server software. The proposed method wraps around the deployed infrastructure and requires no alterations to existing software. This paper discusses the technical encryption issues involved with employing this method. We describe a prototype implementation and motivate the technical choices made. Furthermore, the prototype is validated by applying it to secure the particularly vulnerable Blackboard Learn system, which is a important and critical infrastructural application for our university. We concretely demonstrate how to protect this system against session stealing. Finally, we discuss the application areas of this new method.