Pre-Generated Roaming Keys for Seamless AP Handover
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Solution Overview
Problem
Existing technologies face challenges in achieving seamless roaming by minimizing delays associated with key negotiation during transitions between access points in wireless networks, particularly in ultra-high reliability scenarios.
Innovation Solution
Pre-computing or pre-generating pairwise transient keys (PTKs) for a seamless mobility domain (SMD) before a client roams, allowing these keys to be distributed or stored for immediate use by target access points, thereby eliminating the need for additional key negotiation during the roaming process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If fast transition (FT) key hierarchy is used where PMKs are generated for each access point, then security is improved, but roaming time increases due to nonce exchanges between STA and new AP
Solution Approach 1:
The patent pre-generates pairwise transient keys (PTKs) for all access points in the mobility domain before roaming occurs. The source AP generates PTKs using the root key PMK-R0 and target AP identifiers, then distributes these pre-computed PTKs to respective target APs. This preliminary key generation eliminates the need for time-consuming nonce exchanges during actual roaming, resolving the contradiction between maintaining security through key hierarchy and reducing roaming time.
2Reliability
If 4-way handshake is performed for key generation during roaming, then key security is ensured, but roaming transition time increases
Solution Approach 1:
The patent performs the key generation action in advance by computing PTKs at the source AP using the formula PTK = KDF(PMK-R0, target_AP_MAC, other_parameters) before roaming occurs. These pre-computed keys are distributed to target APs through efficient key distribution mechanisms. During actual roaming, the STA simply uses the pre-established PTK without performing a 4-way handshake, thus maintaining key security while dramatically reducing roaming transition time.
3Reliability
If nonce exchanges are performed between STA and new AP during roaming, then key freshness is achieved, but roaming delay increases
Solution Approach 1:
The patent generates PTKs in advance at the source AP using target AP identifiers and the root key PMK-R0, distributing these pre-computed keys to target APs before roaming occurs. This preliminary action eliminates the need for real-time nonce exchanges between STA and target AP during roaming, achieving both key freshness (through pre-computation using unique target identifiers) and reduced roaming delay.
Data Source
AI summary
A seamless mobility domain (SMD) is described where a PTK for a wireless device is pre-computed or pre-generated before the client roams from a serving AP to a target AP in the SMD. The pre-computed PTK can be distributed (i.e., pushed) to one or more target APs before the wireless device roams, or the PTK can be stored in a key stored and then retrieved from the key store by a target AP once the wireless device roams to the target AP. In another embodiment, the PMK and/or PTK keys are generated using a SMD identifier, such as a SMD MAC address or a special ID for the SMD.