Integration Question : On-die oscillator circuit

[JuneB-Choi]

Hi, I'm June from FADU.
I have some questions about Caliptra HW integration (Caliptra-rtl v1.1).
I have a question about on-die oscillator circuit during Caliptra HW Integration.

1. Why does Caliptra need on-die oscillator circuit?
   Is it used as a defense against external clock attack?

2. If on-die oscillator is not used, what kind of rick is there?
   And do you consider it as a critical security hole in Caliptra integration process?

Thank you,
June.