We could intercept some of the traffic to and from the webpage of our target: www.secret-agency.gov

Unfortunately, the webpage is only available when using a strange encryption.

We believe that the following ciphertext (hexlified) is a GET request to the file /secret.txt, which contains valuable information. However, we were not able to capture the corresponding IV.

ciphertext = 237589eac9a9ee2e02c9cb20ec6843851c60e14420cb0013e1cc7c25188074951d7a3b70b73e4ef9f477caebb9e4e72d05c13a4b4be74e8c26bc7d2dcb374b4f282817910aea5e77a218810190895db51b14c0acd4472178b333eddb5d952a292262f1cf930994103ae18c42f22b28570e245a07ad2f58948aaea7ecfb5cd4f3

Below we have the server's response, a pair of the IV and the ciphertext (hexlified).

IV = 311307825666090033877509447470877887455

ciphertext = 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

Can you recover the encryption key and the file's content for us?

If you really need a starting point here, we have a hint for you: Hint (only if you really need it)