Network Access Control via Preliminary Nonce Negotiation
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Solution Overview
Problem
In computer networks, the tightly-constrained handshake sequence of network protocols, such as DHCP, restricts the exchange of nonce information, making it difficult for endpoint devices to negotiate and verify the integrity of TPM values and nonce values during access control, leading to potential security vulnerabilities like replay attacks.
Innovation Solution
The proposed solution involves an access control device that receives a digital signature based on a TPM value and a nonce value through a tightly-constrained handshake sequence, determines if previously negotiated nonce information and TPM values are acceptable, and verifies the digital signature's validity to grant access rights, even when nonce information cannot be negotiated during the handshake.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a tightly-constrained handshake sequence is used for network access control, then the access control process is faster and more efficient, but the ability to negotiate and verify nonce information is lost, creating security vulnerabilities
Solution Approach 1:
The system performs nonce negotiation and verification before the tightly-constrained handshake sequence begins. The access control device and endpoint device establish and validate nonce values in advance, storing them for later use during the constrained handshake, thereby eliminating security vulnerabilities without compromising the speed of the actual access control process
Solution Approach 2:
The patent introduces an intermediary verification mechanism where the access control device acts as a mediator that holds and validates previously negotiated nonce information. This intermediary role allows the system to maintain security verification capabilities even when the handshake sequence itself is tightly constrained and cannot perform new negotiations
2Reliability
If nonce information negotiation is performed during the handshake sequence, then security verification is improved, but the handshake sequence becomes longer and more complex
Solution Approach 1:
The patent segments the access control process into two distinct phases: a preliminary phase for nonce negotiation and verification, and a subsequent tightly-constrained handshake phase for actual access control. This segmentation allows each phase to be optimized independently - the negotiation phase handles security setup while the handshake phase maintains speed and simplicity
3Loss of information
If more messages are exchanged during the handshake sequence, then more verification data can be transmitted, but the protocol constraints are violated and processing time increases
Solution Approach 1:
All verification information including nonce values is negotiated and transmitted in advance before the tightly-constrained handshake sequence begins. This preliminary action ensures that the complete verification information is available when needed, eliminating the need to extend the handshake sequence with additional message exchanges
Data Source
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AI summary
In general, techniques are described for securely exchanging network access control information. The techniques may be useful in situations where an endpoint device and an access control device perform a tightly-constrained handshake sequence of a network protocol when the endpoint device requests access to a network. The handshake sequence may be constrained in a variety of ways. Due to the constraints of the handshake sequence, the endpoint device and the access control device may be unable to negotiate a set of nonce information during the handshake sequence. For this reason, the access control device uses a previously negotiated set of nonce information and other configuration information associated with the endpoint device as part of a process to determine whether the endpoint device should be allowed to access the protected networks.