Struct KeyManager 

pub struct KeyManager { /* private fields */ }

Manages the rolling window of LogEncryptionKeys used by an crate::encryption::EntryEncryptor.

The “current” key is always used for encryption; on rotation, the old current key is moved into history and a new key takes its place. history is bounded by retention (oldest entries are dropped first once the bound is exceeded). Decryption looks up the right key by the KeyVersion embedded in the payload.

retention of 1 means only the current key is kept; rotating then immediately invalidates the previous key. retention of N means at most N - 1 historical keys plus the current key are retained at any time (so we can decrypt entries from the most recent N versions).

retention is silently clamped to >= 1 at construction time.

Implementations

impl KeyManager

pub fn new(initial: LogEncryptionKey, retention: usize) -> Self

Build a new KeyManager with initial as the current key at KeyVersion 1.

retention is clamped to >= 1; that is, at minimum the current key is always kept. retention = 3 means current + 2 historical keys are retained.

pub fn rotate(&mut self, new_key: LogEncryptionKey) -> KeyVersion

Rotate to a new master key, returning the new current version.

The previous current key is moved into history. When the combined size of (current + history) exceeds retention, the oldest historical entry is dropped.

pub fn current(&self) -> (KeyVersion, &LogEncryptionKey)

The current key, paired with its version.

pub fn lookup(&self, version: KeyVersion) -> Option<&LogEncryptionKey>

Look up the key with version, falling back to historical entries.

Returns None if version is older than the retained window (already pruned) or has never existed.

pub fn version_count(&self) -> usize

Number of versions currently retained (current + history).

Always >= 1 because the current key is always present, so KeyManager does not expose an is_empty method.

pub fn retention(&self) -> usize

Configured retention (always >= 1).