JwAs for Pearl Harbor, there are basically 2 questions that can help us determine whether it was an inside job (of the third type) or not.
- Was the Japanese code cracked prior to the attack on Pearl Harbor?
- Did the Japanese planes approaching Pearl Harbor maintain radio silence with one another?
If the answer to question 1 is "yes, the code was already cracked" and the answer to question 2 is "no, they did not maintain radio silence," then Pearl Harbor was an inside job. It means officials saw the attack coming and let it happen.
Holy shit am I finally able to yap about cryptography on tftv.
Japanese naval codes (i.e. JN-25) were not readable prior to the attack. They were "solved" in the sense that the structure of the code was known, requiring two codebooks that perform grouping and additive operations (will ignore details for now, you can look at this if interested). But without these codebooks it was not functionally readable.
Diplomatic codes were cracked by this time (PURPLE). So the White House certainly knew an attack was coming (it has been a while but I believe primary suspicion was against Macarthur who was not in Hawaii) but there was no clear indication in decoded PURPLE messages that the target was Pearl Harbor*. The infamous 14 part declaration delivered immediately prior to the attack was also not decoded, written down, and delivered in its entirety until about an hour after the attack (and if you read it doesn't really declare an attack officially in Western fashion, just cuts off negotiations. Maybe people who were more used to Japanese sensibilities would know that is equivalent to launching an attack, but still there is no mention of Pearl Harbor. You can read it here.)
Also from a conspiracy theory perspective the motivation to let the attack occur is unclear; wanting to escalate a war with Japan by giving up a critical military keypiece is certainly...a strategy. American neutrality was already a farce by this point in the war with Roosevelt's order to basically shoot to kill German U-Boats so on that front it's not like they need any excuse as well.
*There was correspondence between a spy at Pearl Harbor who reported to the consulate, who would then report to Tokyo. If you know anything about Hawaii there is a large Japanese population there, so his presence is not unusual by any means. One important message that was missed was a request about the location and # of warships at Pearl Harbor. Given the volume of messages being decoded and the people who were actually able to see such messages (notably not the military commander of Pearl Harbor iirc) along with other fuckery that was going on in the cryptography branch it's likely that this was just bad oversight.