The power blogger known as "druking" insists he demonstrated a data manipulation program to South Gyeongsang Province Governor Kim Kyoung-soo in 2016.
The blogger was indicted earlier this year for his involvement in an online opinion rigging scandal, and appeared Friday as a witness at Governor Kim's trial.
He says the governor showed great interest in the program, known as "King Crab" and that encouraged him to further develop it.
While admitting he had visited the blogger, Kim denies having seen a demonstration of the rigging software.
An independent counsel team led by Huh Ik-bum indicted the governor in August on allegations that he and the blogger used data manipulation software before and during last year’s presidential election.