When Spartan Locke refers to Master Chief as 117 in "Halo 2", Arbiter replies that he "was not told" his identity. This directly contradicts with the following cut scene showing the Arbiter's trial, where the Prophet of Truth calls him "Master Chief". This can also be rebutted in Halo 3, where other people in the presence of the Arbiter call Master Chief by this name including but not limited to Sergeant Johnson.
However The Arbiter wasn't referring to the fact he was unaware of the Chief's identity when talking to Spartan Locke, he was referring to the fact he was not aware Locke was looking for the Master Chief, he had only been told Locke was looking for a Spartan before Locke came to see him.
However The Arbiter wasn't referring to the fact he was unaware of the Chief's identity when talking to Spartan Locke, he was referring to the fact he was not aware Locke was looking for the Master Chief, he had only been told Locke was looking for a Spartan before Locke came to see him.