If R2 is configured with simple authentication you can see the key in ospf hello. Take a packet capture on R1 and check the hello from R2.
If R2 is using MD5, you can get the hash only.
Taking a pcap on SRX will help you to identify this.
below commad can be used to capture the ospf hello, files will be written into your home directory.
user@host> monitor traffic interface ge-x/x/x matching "proto 89" write-file ospf.cap extensive
I have attached a sample capture .
Thanks,
Suraj
Please Mark My Solution Accepted if it Helped, Kudos are Appreciated too