Module index 

Session Index Allocator

Manages allocation of 32-bit session indices for O(1) packet dispatch. Each Noise session receives a unique index chosen by the receiver; incoming encrypted packets include the receiver’s index for fast lookup.

Design

• Indices are random (cryptographically secure) to prevent guessing
• Unique per transport to avoid collision between transports
• 32-bit space supports ~65K concurrent sessions before birthday collision
• Indices are rotated on rekey for anti-correlation

Wire Format

Encrypted frames include receiver_idx for session lookup:

[0x00][receiver_idx:4 LE][counter:8 LE][ciphertext+tag]

Structs

IndexAllocator

Allocator for session indices within a single transport.

SessionIndex

A 32-bit session index.

Enums

IndexError

Errors related to index allocation.