The question I immediately had was where did ‘Undid iridium’ come from as Halsey’s password? It sounds like some Harry Potter nonsense.
The Halo Bulletin has some kind of answer as Brian Reed, the writer of Spartan Operations explains:
“The backdoor password Halsey says originated from an accidental text I sent to my wife one afternoon. I didn't realize my phone was awake and I entered some gibberish that autocorrected to "Undid iridium" and sent itself. Lucky me, I'd just written Halsey and Roland's scene the day before, and I'd had no idea what her secret phrase should be in that moment. The original draft of the script was "[CLEVER PASSWORD]". “
This of course does not explain how Halsey knew the password for Roland in the first place…