When we have a proxy and a Zabbix agent using PSK encryption, we can bring down the Zabbix proxy connection from the Data Collection | Hosts configuration page simply by editing the PSK key. In all fairness this does require us to know the proxy PSK identity, but in all fairness a lot of customers use the name of the proxy as the PSK identity.

Steps to reproduce:

1. Create encrypted proxy (identity: prox_psk) [PSK key: 123456]
2. Create encrypted Zabbix agent (identity: prox_psk) [PSK key: 123456]
3. Both proxy and agent will be connected correctly and sending data
4. Change Zabbix agent PSK key in the Zabbix frontend (identity: prox_psk) [PSK key: 456789]
5. Proxy connection goes down