Passive attack

Abstract: In this paper we consider low latency connection-based anonymity systems which can be used for applications like web browsing or SSH. Although several such systems have been designed and built, their anonymity has so far not been adequately evaluated.

Abstract: This paper presents a protocol called SAKE (Software Attestation for Key Establishment), for establishing a shared key between any two neighboring nodes of a sensor network. SAKE guarantees the secrecy and authenticity of the key that is established, without requiring any prior authentic or secret information in either node. In other words, the attacker can read and modify the entire memory contents of both nodes before SAKE executes. Further, to the best of our knowledge, SAKE is the only protocol that can perform key re-establishment after sensor nodes are compromised, because the presence of the attacker's code in the memory of either protocol participant does not compromise the security of SAKE. Also, the attacker can perform any active or passive attack using an arbitrary number of malicious, colluding nodes. SAKE does not require any hardware modification to the sensor nodes, human mediation, or secure side channels. However, we do assume the setting of a computationally-limited attacker that does not introduce its own computationally powerful nodes into the sensor network. SAKE is based on ICE (Indisputable Code Execution), a primitive we introduce in previous work to dynamically establish a trusted execution environment on a remote, untrusted sensor node.

Abstract: In this paper we consider low-latency connection-based anonymity systems which can be used for applications like web browsing or SSH. Although several such systems have been designed and built, their anonymity has so far not been adequately evaluated. We analyse the anonymity of connection-based systems against global passive adversaries. We give a precise description of a packet-counting attack which requires a very low degree of precision from the adversary, evaluate its effectiveness against connection-based systems depending on their size, architecture and configuration, and calculate the amount of traffic necessary to provide a minimum degree of protection. We then present a second attack based on tracking connection starts which gives us another lower bound on traffic volumes required to provide at least some anonymity.

Abstract: This paper presents a protocol called Software Attestation for Key Establishment (SAKE), for establishing a shared key between any two neighboring nodes of a sensor network. SAKE guarantees the secrecy and authenticity of the key that is established, without requiring any prior authentic or secret cryptographic information in either node. In other words, the attacker can read and modify the entire memory contents of both nodes before SAKE executes. Further, to the best of our knowledge, SAKE is the only protocol that can perform key re-establishment after sensor nodes are compromised, because the presence of the attacker's code in the memory of either protocol participant does not compromise the security of SAKE. Also, the attacker can perform any active or passive attack using an arbitrary number of malicious, colluding nodes. SAKE does not require any hardware modification to the sensor nodes, human mediation, or secure side channels. However, we do assume the setting of a computationally-limited attacker that does not introduce its own computationally-powerful nodes into the sensor network. SAKE is based on Indisputable Code Execution (ICE), a primitive we introduce in previous work to dynamically establish a trusted execution environment on a remote, untrusted sensor node.