Struct SessionCipher 

pub struct SessionCipher { /* private fields */ }

Symmetric cipher for encrypting/decrypting frames within a session.

Uses AES-256-GCM with an incrementing nonce counter to prevent reuse. The nonce is constructed as: 8-byte random session prefix || 4-byte counter.

Replay protection: decrypt tracks the highest accepted counter and rejects any frame whose counter is ≤ the last accepted value.

Implementations

impl SessionCipher

pub fn new(key: &[u8; 32], nonce_prefix: [u8; 8]) -> Self

Create a new SessionCipher from a 32-byte key and 8-byte nonce prefix.

pub fn encrypt(&self, plaintext: &[u8]) -> Result<EncryptedFrame, SessionError>

Encrypt plaintext, returning the nonce and ciphertext.

pub fn decrypt(&self, frame: &EncryptedFrame) -> Result<Vec<u8>, SessionError>

Decrypt an encrypted frame.

Rejects replayed frames: the counter embedded in frame.nonce[8..12] must be strictly greater than the last accepted counter.

pub fn encrypt_in_place_detached( &self, payload: &mut [u8], ) -> Result<([u8; 12], [u8; 16]), SessionError>

Encrypts plaintext in-place, returning the generated nonce and tag. Returns an error if the nonce counter is exhausted or encryption fails.

pub fn decrypt_in_place_detached( &self, nonce_bytes: &[u8; 12], payload: &mut [u8], tag_bytes: &[u8; 16], ) -> Result<(), SessionError>

Decrypts a frame in-place, avoiding an allocation. Returns an error if the nonce is replayed, or if decryption fails.