Knuckle_Buster

In this challenge, two individuals—Alice and Bob—are communicating in secret. They use the Diffie-Hellman key exchange protocol to protect their communication. I will provide you with enough information to decrypt a message intercepted between them. All you need to do is calculate the shared secret and decrypt it to get the flag.

Here is the encrypted flag. It was encrypted using AES-256-CBC, with SHA-256 for key derivation and a prepended 16 byte IV.

publicA -----BEGIN PUBLIC KEY----- MIGaMFMGCSqGSIb3DQEDATBGAkEAiBB/FlC3W8aPLJxYGXzKsnpEmPKIKR4JetlA1ky+TKTYofXUKSFucGxtrmWlVFjnLZUqJFjj0bVDKSiYOfod1wIBAgNDAAJAN3YrjXtIssyugO9tQ3BRy2TN92Qkhkp/VP5zfLEMQg1AE/YofkCIc/KSZOBpuroiQoCK0qTNkD4HzCzDa7ap5Q== -----END PUBLIC KEY-----

privateB -----BEGIN PRIVATE KEY----- MIGcAgEAMFMGCSqGSIb3DQEDATBGAkEAiBB/FlC3W8aPLJxYGXzKsnpEmPKIKR4JetlA1ky+TKTYofXUKSFucGxtrmWlVFjnLZUqJFjj0bVDKSiYOfod1wIBAgRCAkBSsgvp3xivPK6Wp2X+SIjGllg1MT4zJdEoyUjV6iDLGytdeLpokYOO6xsGIiVb8b6A/5onnopra2iXBb0dS5rn -----END PRIVATE KEY-----

dhparam -----BEGIN DH PARAMETERS----- MEYCQQCIEH8WULdbxo8snFgZfMqyekSY8ogpHgl62UDWTL5MpNih9dQpIW5wbG2uZaVUWOctlSokWOPRtUMpKJg5+h3XAgEC -----END DH PARAMETERS-----

Right Click, Save As.... Encrypted Flag