http://terminus.i2p/r/i2p/34/36/2
The public key representing a router identity for broadcast which contains a lease set, these include the inbound and outbound tunnels (we'll call 1, 2, 3, and 1a, 2a, 3a with the latter being the inbound for this user), the floodfills use the distributed hash table to pull whatever the public key is thats assigned to the leaseset for the receiver and they use their own (1, 2, 3 and 1a, 2a, 3a) for the inbound and outbound traffic back to the receiver requesting this.