The correspondence of Fatih Gürsul, an adviser to the opposition Republican People's Party (CHP) head Kemal Kılıçdaroğlu and a Gülenist Terror Group (FETÖ) figure, show how he received orders from the group.

Gürsul was detained last December as part of a probe into the terrorist group's infiltrators in universities. An associate professor at Istanbul University, Gürsul was also dismissed from his post following a coup attempt last year blamed on the terrorist group.

One of the most serious allegations towards Gürsul involves his use of ByLock, an encrypted messaging app exclusively used by FETÖ. His correspondence with a senior FETÖ "brother," identified only as A.H.P. by security sources, shows he sought advice from the group for everything he did and shared his emails to Kılıçdaroğlu with FETÖ members.

The messages between 2014 and 2015 indicate that Gürsul was "ready to obey any orders" from A.H.P., a point man for FETÖ leader Fetullah Gülen. Like Gülen, A.H.P. resides in the United States.

Investigators say they detected at least 256 messages sent by Gürsul, which indicate that he sought advice from FETÖ on what to do in his post as a CHP adviser before a critical election. In one message, he requests a date to visit Gülen in the United States. In another message, he said he would help Kılıçdaroğlu more ahead of an early election.

A message sent by Gürsul, while he was apparently abroad, says Kılıçdaroğlu sent him an email. In the email, Kılıçdaroğlu tells Gürsul he is "sad about what's happening in Turkey." "Undoubtedly, you are concerned about what is going on," Kılıçdaroğlu says in his email according to Gürsul's intercepted Bylock message.

Testimony from Gülenists in the bureaucracy, detained after the July 15 putsch attempt, pointed to the prevalence of the app's use. Prosecutors say ByLock was popular among Gülenists for secret communications between 2013 and 2015, and after 2015, the terror cult turned to Eagle IM, which offered "256-bit end-to-end AES encryption" for its users.

The ByLock codes were broken in August by the Turkish National Intelligence Agency (MIT), resulting in 60,000 members being uncovered. Another encrypted messaging app, Eagle, was also deciphered by intelligence officers recently.