System and method for cryptographic continuity assertions

A method for maintaining secure session continuity between a client device and a remote server, the method comprising:

• storing, in a hardware-backed or software-based security module, a non-exportable or extraction-restricted cryptographic key, the security module performing cryptographic operations in a serialized manner consistent with exclusive-access execution characteristics;
• generating, by a client-side execution environment operating in foreground and background execution states and subject to platform-controlled behaviors such as background-execution suspension, timer adjustments, deferred scheduling, or network-wake constraints, a continuity assertion payload including a timestamp, counter, nonce, monotonic value, or other freshness indicator;
• maintaining freshness indicators during offline intervals using mechanisms that preserve monotonic ordering;
• obtaining, from the security module, a cryptographic proof-of-possession over the continuity assertion payload, including coordinating secure-element access with user-initiated cryptographic operations and serialized secure-element execution characteristics;
• transmitting or embedding, within client-to-server communication, a cryptographic continuity assertion at a predetermined interval or in response to a server-initiated or event-triggered liveness request, including authenticated delivery over one or more communication channels having differing availability, timing, or platform-controlled wake characteristics;
• reconciling locally maintained freshness indicators with server-maintained freshness indicators upon reconnection, including transmitting a continuity assertion within a server-defined or otherwise applicable freshness-validation window;
• and adjusting session validity at the remote server based on whether a cryptographic continuity assertion is received and satisfies verification and freshness-validation requirements.

A non-transitory computer-readable medium storing instructions that, when executed by a processor of a client device, cause the client device to:

• store, in a hardware-backed or software-based security module, a non-exportable or extraction-restricted cryptographic key, the security module performing cryptographic operations in a serialized manner consistent with exclusive-access execution characteristics;
• generate, within a client-side execution environment capable of foreground and background execution and subject to platform-controlled behaviors such as background-execution suspension, timer adjustments, deferred scheduling, or network-wake constraints, a continuity assertion payload including a timestamp, counter, nonce, monotonic value, or other freshness indicator;
• maintain freshness indicators during offline intervals using mechanisms that preserve monotonic ordering;
• obtain, from the security module, a cryptographic proof-of-possession over the continuity assertion payload, including coordinating secure-element access with user-initiated cryptographic operations and serialized secure-element execution characteristics;
• transmit or embed, within client-to-server communication, a cryptographic continuity assertion at a predetermined interval or in response to a server-initiated or event-triggered liveness request, including authenticated delivery over one or more communication channels having differing availability, timing, or platform-controlled wake characteristics;
• reconcile locally maintained freshness indicators with server-maintained freshness indicators upon reconnection, including transmitting a continuity assertion within a server-defined or otherwise applicable freshness-validation window;
• and maintain session validity only when the remote server successfully verifies the cryptographic proof-of-possession, evaluates freshness indicators, and evaluates delivery-context information associated with the continuity assertion.