http://terminus.i2p/r/i2p/34/36/2
The most common explanation of I2P I have seen is the public keys assigned to each user and private keys which are not published. 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...