Reversible Sneaky Algorithm #2

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PART 1 : CHALLENGE DESCRIPTION

Oligar was thinking about number theory at AwesomeMath when he 
decided to encrypt a message with RSA. As a mathematician, he made 
various observations about the numbers. He told Molly one such 
observation:

a^r ≡ 1 (mod n)

He isn't SHOR if he accidentally revealed anything by telling Molly 
this fact... can you decrypt his message?

Source code, a and r, public key, and ciphertext are attached.

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PART 2 : GIVEN FILES

[>] oligarchy.pem

-----BEGIN PUBLIC KEY-----
MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQC5a2J4gIZo3mzj0LdTFbESkwD+
tIuiM1Pwl7Z8Aj+9zdDmMIbujHEamxU+osKjEh/BQeJ6fWYucrjDHliQoDFL6Soy
jti228yQw9fwp13IwTsPQao0d2JTZQ36J9PDgJuBv7EDo1bsJ2G23SM1SaIrqzMi
QJI0LnAnlkxwqePuywIDAQAB
-----END PUBLIC KEY-----

[>] are_you_shor.txt

a	84733215803103612460901465701232424798609470209825913961212238457798293111098195061837071495218083197429913141798442522950831495758395873695688189182925448736211066067276791533151828542439575601763801135131479532656528730453020404557236783254278625529895480234633323403399468237577058553920576024305830379725
r	21700996784810065805847020455080940987640304282783092123992896363328128691169420271855815648912121417792054646557156071514079520782530801688062034321252682229729442734741486715339008457753023855600772948737800521010217600436912058582658334252483984244806083617513596479033871117464319239681526924092910597300
c	85407181759755287105309527383534372436668736072315927293076398182206068631971587183149437554341349819060482477969350837066653250734556920049021810122548703168301872412719117857995283679569989680329696657609285728934732302846152702363240223251805773071022405764521081142920227557091217872210813095318042763847

[>] shor.py

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PART 3 : GETTING THE FLAG

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FLAG : nactf{d0wn_wi7h_7h3_0lig4rchy}