Verifying Cryptographic Identity in SIP Media Sessions
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Solution Overview
Problem
Session Initiation Protocol (SIP) signaling through proxies and Session Border Controllers (SBCs) obscures endpoint information, making it difficult to verify cryptographic identities during media session initialization, as SBCs modify message fields like IP addresses and ports, potentially leading to identity authentication challenges.
Innovation Solution
A method involving authentication agents that create and verify signatures using private and public keys to authenticate endpoints, ensuring the identity of the originating endpoint is confirmed before initiating a media session, even if message fields are modified by SBCs, by signing specific fields and using certificates to challenge and confirm the private key ownership.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If SIP signaling is routed through proxies and Session Border Controllers (SBCs) for network management and media traffic policing, then network control and security are improved, but endpoint identity verification becomes difficult because SBCs modify message fields like IP addresses and ports
Solution Approach 1:
The patent applies preliminary action by having the originating endpoint sign the identity assertion message with its private key before the message passes through SBCs. This signature is created in advance to protect the identity information from being altered or forged by intermediate network elements, ensuring that the endpoint's true identity is preserved throughout the signaling path.
Solution Approach 2:
The patent introduces certificates as an intermediary mechanism for identity verification. The recipient endpoint uses certificates to verify the signature on the identity assertion message, acting as a trusted mediator that enables secure verification without requiring direct trust between endpoints. This intermediary layer solves the verification problem created by SBCs modifying message fields.
2Reliability
If SBCs modify message fields such as IP addresses and ports for network management purposes, then network security and traffic control are improved, but the integrity of endpoint identity information is compromised
Solution Approach 1:
The originating endpoint performs preliminary signing of the identity assertion message with its private key before the message enters the network infrastructure. This pre-signing ensures that even if SBCs modify other fields in the message, the core identity assertion remains cryptographically protected and tamper-evident.
Solution Approach 2:
The patent extracts the identity assertion from the modifiable message fields and protects it separately through cryptographic signing. By separating the identity verification mechanism from the SBC-modifiable message content, the system ensures that identity integrity is maintained independently of network management modifications.
3Reliability
If cryptographic signatures are used to protect identity assertions from SBC modifications, then identity verification reliability is improved, but the complexity of the authentication process increases
Solution Approach 1:
The patent uses certificates as an intermediary that simplifies the verification process. Instead of requiring the recipient endpoint to directly verify complex cryptographic signatures, the certificate acts as a trusted intermediary that encapsulates verification logic, making the process more manageable while maintaining strong security guarantees.
Solution Approach 2:
The certificate verification is performed as a preliminary action before media session establishment. By handling the cryptographic verification upfront during session initialization, the patent avoids adding ongoing complexity to the media transmission process itself, concentrating the computational burden in a controlled initial phase.
Data Source
AI summary
An authentication agent may cryptographically identify a remote endpoint that sent a media initialization message even though intermediate devices may modify certain fields in the message after a signature is inserted. The originating endpoint's agent may create the signature over some fields of the message using an enterprise network's private key. The agent may insert the signature into the message and send the message to a recipient endpoint's authentication agent. The recipient agent may verify the signature, receive a certificate including a second public key, and challenge the identity of the originating endpoint in order to confirm that identity. This challenge may request a confirmation that the originating endpoint knows the private key corresponding to the second public key and may occur while running encrypted media at the endpoints. After the originating endpoint is authenticated, the endpoints may exchange encrypted and/or unencrypted media.