Short explanation: the password is "block"
Use command "connect 3"
Use the command "unlock block"
Vion's Cage will unlock
This is the long explanation (What the game wants you to do):
First, you use the command "connect" and type "3" this will connect you to the cage
Connect 3
Type and send the command help, this will show you the available commands.
Use the command "unlock" and just send it. Then use the command "monitor" Which will show you the last memory access. Since you used the unlock command, and the password is stored in the memory, the last access is from "unlock". It will show this:
Last memory access at [6,8](5 bytes read) by 'unlock'
Then just check the cell in (6,8), which contains the word "block" this is the password
Finally, type the command "unlock block" and it will unlock Vion's Cage
Sorry 4 my english