Secure User Identification
From AMule Project FAQ
What is Secure User Identification (SUI) ?
Clients in the network are identified by a unique value called user hash. This user hash is stored in the preferences.dat file and is used to grant earned credits with other users. aMule (like eMule) can use an asymmetric encryption to avoid exploiting or manipulating other user hash values. The method uses a private and a public key to ensure a correct and unique identification on other clients.
Secure User Identification can be turned on in Preferences -> Connection (since aMule 2.x). It is recommended to use it.
The identification process goes as follows: