Function construct_nonce 

pub fn construct_nonce(
    epoch: u32,
    direction: Direction,
    counter: u64,
) -> [u8; 24]

Available on crate feature crypto only.

Construct a 24-byte XChaCha20-Poly1305 nonce.

Layout:

[ epoch (4) | direction (1) | zeros (11) | counter (8) ]

Arguments

• epoch - Current key epoch (increments on rekey)
• direction - Communication direction
• counter - Per-direction frame counter