Stateless Symmetric Encryption: Session Keys Derived From Current Identity State

Mechanism

Stateless symmetric encryption removes the stored session key from the protocol. Instead of agreeing on and retaining a long-lived key, both endpoints derive a transient symmetric key from the recipient's current dynamic identity. The sender derives the key by applying a key-derivation function to the recipient's current dynamic identity, selected from the recipient's dynamic device hash (DDH_R) or dynamic agent hash (DAH_R), together with a domain-separating context. The sender then performs authenticated encryption over the payload and constructs a message comprising a transport-layer header that carries the sender's current dynamic hash and an encrypted payload. The message does not include the symmetric encryption key.

The recipient identity used for key derivation may originate from a local-state vector processed through an extractor, from a hardware anchor combined with a volatile salt, or from a hybrid that combines both mechanisms into a single identity value. Because the key is bound to the recipient's memory-resolved identity state at the time of transmission rather than to a persistent secret, the construction operates without certificate authorities, persistent keypairs, or synchronized registries.

The Embedded Sender Hash

Identity is bound at both the transport and the semantic layer. The sender places its current dynamic hash in the message header for fast, stateless screening at the receiver, and embeds an additional copy of the sender's current dynamic agent hash (DAH_S) inside the ciphertext for payload-layer verification. The header value enables rapid screening before any cryptographic work, while the payload-embedded value provides content-layer authentication that is recoverable only by a recipient that can decrypt.

This dual placement is what lets the receiver reject malformed traffic before decryption and prevent man-in-the-middle substitution after decryption. A header value can be inspected cheaply and rejected if it is not a valid successor on the sender's trust slope. An embedded value is recoverable only from a payload that decrypts under the recipient's identity-derived key, so it cannot be supplied by an adversary who cannot produce that ciphertext.

Two-Stage Validation

Upon receipt the recipient performs a two-stage validation procedure. In the first stage, the dynamic agent hash presented in the message header is checked against the last trusted successor stored locally using a lightweight continuity test, confirming that the incoming header value is a valid successor on the sender's trust slope. This screening precedes any decryption. If continuity cannot be confirmed immediately, the recipient may defer the decision until a bounded proof or checkpoint is obtained. If continuity is validated, the recipient derives a decryption key from its own current identity and attempts payload decryption. Successful decryption demonstrates that the encrypted payload was generated for the correct memory-resolved identity state of the recipient at the time of transmission.

In the second stage, following decryption, the recipient extracts the embedded sender dynamic agent hash from the plaintext and validates it as the expected successor on the sender's trust slope under policy-bounded continuity rules. This payload-layer verification provides semantic authentication independent of the transport header, ensuring that both routing-layer and content-layer integrity requirements are satisfied before the message is accepted. The message is accepted only upon successful validation of both the header-level dynamic hash and the embedded sender hash. If either validation fails, the recipient records a rejection, may degrade the sender's trust score according to local policy, and may quarantine the message or sender for review.

Fully Stateless Operation

This architecture permits fully stateless operation. Neither sender nor recipient maintains a long-lived session key. Instead, all symmetric keys are derived transiently from identity values produced by the dynamic update rule. When identity is produced through a local-state vector, stability-tuned projections and error-tolerant sketches prevent benign fluctuations in local measurements from causing unnecessary decryption failures, while substantive role or context changes intentionally alter the recipient identity and force rekeying. When identity is produced from a hardware anchor and volatile salt, freshness is maintained by the non-repeating salt. Hybrid implementations combine both sources to improve robustness across heterogeneous device classes and environmental conditions.

An implementable embodiment performs derivation at the sender using a domain-specific context string and applies authenticated encryption to the payload while embedding the sender's dynamic agent hash inside the ciphertext. At the receiver, an equivalent derivation from the recipient's current identity reconstructs the symmetric key needed to decrypt, after which the embedded dynamic agent hash is validated against the stored sender trust slope. Header validation, identity-derived key construction, payload decryption, embedded-hash comparison, and the associated failure logic proceed as process flows defined entirely by the memory-native identity substrate and local policy rather than by hardware-level coupling.

Fallback When Identity Is Stale

A sender does not always possess the recipient's most recent identity value. In that case the sender derives the symmetric key from the most recently trusted recipient anchor or epoch and transmits an initial attempt under a bounded rekey failure tolerance. If decryption fails, the sender performs a fallback consisting of either a short challenge-response rekey exchange scoped to the recipient's current epoch, or a checkpoint request sufficient to reconstruct a successor window to the recipient's current identity. Once the sender obtains the updated recipient identity, the two-stage authentication proceeds without dependence on external certificate authorities or persistent key-exchange state.

Where header-level continuity validation succeeds but payload decryption fails because of drift in the recipient's identity, the recipient advertises its current anchor or checkpoint, and the sender retries once using that anchor before requesting a bounded checkpoint response. Retries are limited to a fixed attempt window to avoid oracle leakage while still enabling recovery from sparse state.

Threat Surface

Stateless symmetric encryption composes with the broader Dynamic Signature Mesh threat model, which treats identity as a progressing trust slope rather than a set of persistent keys. Resistance to static-key compromise arises from the absence of persistent secrets: each dynamic hash is ephemeral, non-reusable, and meaningful only as part of a monotonic sequence anchored in a previously trusted state. Decryption keys derived from the recipient's current identity bind confidentiality and integrity to memory-resolved state, ensuring deterministic rejection of malformed or substituted messages.

Receivers support a two-epoch acceptance window and per-sender rate limits to mitigate denial-of-service conditions when senders encrypt using stale identities. Header-level continuity screening discards off-slope traffic early, before any decryption is attempted, and replay controls reject repeated or regressed successors. Failure responses reveal nothing about rekey status, so a failed attempt does not disclose whether the recipient has advanced its identity, and repeated failures degrade trust or trigger checkpoint-based retries.

Isolation From Legacy Paths

Where interoperability with legacy PKI-based systems is required, it is confined to a segregated adapter so that it cannot affect the identity-derived encryption path. A legacy-bridge adapter generates a temporary keypair and a session nonce under a domain-separated context and derives a transient, session-scoped fallback identifier, maintained entirely within an isolation boundary that prevents any interaction with the trust-slope update rules. Fallback identifiers and their PKI signatures never influence dynamic hash evolution. Any attempt to inject PKI material into a dynamic hash, or to export dynamic hash internals to satisfy a legacy requirement, results in closed-fail termination. The identity-derived encryption mechanism therefore never inherits the key-storage, revocation, or correlation surfaces of the legacy path it bridges.

Disclosure Scope

Stateless symmetric encryption, comprising derivation of a symmetric key from the recipient's current dynamic device hash or dynamic agent hash together with a domain-separating context, authenticated encryption of the payload with the sender's dynamic agent hash embedded inside the ciphertext, the transport header carrying the sender's current dynamic hash, the two-stage validation that screens the header before decryption and validates the embedded sender hash after decryption, the fully stateless operation in which no long-lived session key is retained, and the bounded rekey and checkpoint fallback for stale recipient identities, is disclosed in U.S. Application No. 19/388,580 at Section 3, with the associated threat surface and legacy isolation described in Sections 13 and 14. This article describes that disclosed mechanism. The scope extends to local-state, hardware-anchor, and hybrid sources for the recipient identity used in derivation, provided the symmetric key remains derived transiently from a memory-resolved identity value and no persistent key material is introduced.