Improper Isolation of Shared Resources in Network On Chip (NoC)

Stable Base

Structure: Simple

Description

This vulnerability occurs when a Network on Chip (NoC) fails to properly separate its internal, shared resources—like buffers, switches, and channels—between trusted and untrusted components. This lack of isolation creates a timing side-channel, allowing untrusted agents to potentially infer sensitive data from trusted ones.

Extended Description

Network on Chips are designed with many shared internal resources to handle data packets from different sources. When resources like internal buffers, crossbars, individual ports, and communication channels are not securely partitioned between trusted and untrusted domains, they become points of contention. This shared access introduces interference, which an attacker can measure and analyze to create a timing channel, potentially leaking information about the trusted agent's activities. The security threat here is twofold. First, it directly enables side-channel attacks where an attacker can deduce sensitive information by observing timing variations. Second, this improper isolation can cause significant performance degradation, as network interference from untrusted domains reduces overall system throughput and increases latency for legitimate traffic.

Common Consequences 1

Scope: ConfidentialityAvailability

Impact: DoS: Resource Consumption (Other)Varies by ContextOther

Attackers may infer data that belongs to a trusted agent. The methods used to perform this attack may result in noticeably increased resource consumption.

Detection Methods 1

Manual AnalysisModerate

Providing marker flags to send through the interfaces coupled with examination of which users are able to read or manipulate the flags will help verify that the proper isolation has been achieved and is effective.

Potential Mitigations 1

Phase: Architecture and DesignImplementation

Implement priority-based arbitration inside the NoC and have dedicated buffers or virtual channels for routing secret data from trusted agents.

Demonstrative Examples 1

Consider a NoC that implements a one-dimensional mesh network with four nodes. This supports two flows: Flow A from node 0 to node 3 (via node 1 and node 2) and Flow B from node 1 to node 2. Flows A and B share a common link between Node 1 and Node 2. Only one flow can use the link in each cycle.

One of the masters to this NoC implements a cryptographic algorithm (RSA), and another master to the NoC is a core that can be exercised by an attacker. The RSA algorithm performs a modulo multiplication of two large numbers and depends on each bit of the secret key. The algorithm examines each bit in the secret key and only performs multiplication if the bit is 1. This algorithm is known to be prone to timing attacks. Whenever RSA performs multiplication, there is additional network traffic to the memory controller. One of the reasons for this is cache conflicts.

Since this is a one-dimensional mesh, only one flow can use the link in each cycle. Also, packets from the attack program and the RSA program share the output port of the network-on-chip. This contention results in network interference, and the throughput and latency of one flow can be affected by the other flow's demand.

Code Example:

Attack

The attacker runs a loop program on the core they control, and this causes a cache miss in every iteration for the RSA algorithm. Thus, by observing network-traffic bandwidth and timing, the attack program can determine when the RSA algorithm is doing a multiply operation (i.e., when the secret key bit is 1) and eventually extract the entire, secret key.

There may be different ways to fix this particular weakness.