# Ephemeral keys Ephemeral keys are generated during the process of notes encryption. The symmetric cipher algorithm ([ChaCha20Poly1305](https://datatracker.ietf.org/doc/html/rfc8439)) which applies to the memo block is required to use different keys for security reasons. They are derived from the random secret keys generated before the each encryption operation. The account's intermediate key is used for the derivation process. * The **receiving key** is a set of the intermediate key $$\eta$$ and ephemeral public key $$A\_i$$. These are used to derive the note encryption key. Successfully decrypted notes with the $$\eta$$ key are considered received notes by a client. --- # Agent Instructions: 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: ``` GET https://docs.zkbob.com/implementation/zkbob-keys/ephemeral-keys.md?ask= ``` The question should be specific, self-contained, and written in natural language. 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.