> For the complete documentation index, see [llms.txt](https://cifer.gitbook.io/cifer-docs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://cifer.gitbook.io/cifer-docs/documentation/cifer-sdk/architecture-and-security/freshness-and-replay-protection.md). # Freshness and replay protection Every authenticated Blackbox operation signs a canonical request string containing context such as chain, secret, signer, freshness value, and operation data. ## Web3 The SDK fetches a recent block number from the configured read client. The Blackbox accepts requests only within its freshness window. Recognized stale-block responses can be retried with a new height. ## Web2 Web2 uses `WEB2_CHAIN_ID = -1` and a millisecond timestamp rather than an RPC block. The active session signs the request. ## Integration rules * Use the SDK's canonical signing helpers; do not invent a new string format. * Keep the read client on the same chain as the target SecretsController. * Synchronize server and client clocks for Web2 deployments. * Do not cache a signed request for later reuse. * Treat repeated stale errors as an RPC, environment, or time-synchronization problem. * Preserve SDK error types so the UI can distinguish retryable failures from rejected authorization. Freshness reduces replay risk but does not replace TLS, authorization, session revocation, or transaction nonce controls. --- # Agent Instructions This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com. ## Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter: ``` GET https://cifer.gitbook.io/cifer-docs/documentation/cifer-sdk/architecture-and-security/freshness-and-replay-protection.md?ask=&goal= ``` `ask` is the immediate question: it should be specific, self-contained, and written in natural language. `goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.