Struct SFrameSession 

pub struct SFrameSession { /* private fields */ }

An SFrame session bound to one MLS epoch.

A new session must be created whenever the MLS group commits (epoch changes) — the old base key becomes unreachable and all per-sender keys are rotated automatically.

Owns the per-leaf encryptor state for this epoch: repeated calls to encryptor for the same leaf_index return a handle to the same counter, never a fresh one, so callers cannot accidentally reuse a (key, KID, CTR) nonce by recreating a handle (e.g. one per thread, or on every request).

Implementations

impl SFrameSession

pub fn new(base_key: [u8; 32], epoch: u64, suite: CipherSuite) -> SFrameSession

Creates a session from a raw 32-byte base key.

Prefer from_mls when an MlsContext is available; this constructor is mainly for testing.

pub fn from_mls( mls: &MlsContext, label: &str, suite: CipherSuite, ) -> Result<SFrameSession, SFrameError>

Derives a session from the current MLS group state.

Calls MLS.ExportSecret(label, context=epoch_be8, length=32) to obtain the base key, then stores it alongside the current epoch and ciphersuite.

label is application-defined (e.g. "gbp/sframe v1").

pub fn epoch(&self) -> u64

Returns the MLS epoch this session was created for.

pub fn suite(&self) -> CipherSuite

Returns the active ciphersuite.

pub fn encryptor(&self, leaf_index: u32) -> SFrameEncryptor

Returns a sender-side encryptor handle for leaf_index.

The returned SFrameEncryptor holds the derived key+salt for this sender and shares its counter with every other handle returned for the same leaf_index on this session - calling this repeatedly (one per thread, one per request, …) is safe and will never produce two independent counters for the same KID.

pub fn decryptor(&self) -> SFrameDecryptor

Creates a receiver-side decryptor for this epoch.

The SFrameDecryptor lazily derives per-sender keys as new KIDs arrive, and maintains an independent 1024-entry replay window per sender.