ISIS was behind the Kerman attack. Iran still blames Israel and the United States, though.

"The January 3 terror attack in Iran claimed by the Islamic State of Iraq and al-Sham (ISIS) was the deadliest since the 1979 Islamic Revolution. Even after the Iranian government revised the total number of deceased persons—at least ninety—downward from 103, it was still higher than the mortalities from the bombing of the Islamic Republican Party’s headquarters in 1981, which resulted in the death of around seventy-four people. The former’s significance will require the Islamic Republic’s establishment to respond, but it will likely do so in a deliberate manner. After ISIS attacks, there is a pattern in the Islamic Republic of publicly blaming the United States and its allies while focusing its kinetic retaliation on ISIS itself."