"People like Saharkhiz are considered even more dangerous than those opposing the regime from outside," he added.
As the elder Saharkhiz languished in prison in 2009, his son Mehdi became an opposition activist from the relative safety of exile in New Jersey.
Using Twitter, Facebook and YouTube, Mehdi distributed amateur videos smuggled from Iran showing Iranian security forces beating and arresting demonstrators.
"The least I can do is get their voices out," he said, in a 2010 interview with CNN.
Election of Rouhani may have had impact
Mehdi has lived in the United States for many years, and last year became a naturalized American citizen. His father was stationed in New York for several years in the 1990s while working for IRNA, the official Iranian news agency. During that time, Mehdi attended high school in suburbs outside New York City.
Four years after his arrest, the elder Saharkhiz said there was no formal reason given for his release. But he said the move was likely linked to the recent election of Hassan Rouhani to the post of president.
Several other dissidents detained during the 2009 crackdown were released last month, according to the English-language daily Tehran Times. The Iranian government never issued a formal explanation for why these political prisoners were freed.
Rouhani campaigned on a platform of reform and an end to Iran's international isolation. Last month, he called for a negotiated end to Tehran's long feud with Washington over its nuclear program. His charm offensive during a visit to the United Nations General Assembly climaxed with a brief phone conversation with Barak Obama. It was the first direct contact between American and Iranian presidents in more than 30 years.
"Not the system, but the situation has changed," explained Isa Saharkhiz, during his interview with CNN.
Though optimistic about Rouhani's presidency, Saharkhiz warned that Iran was a "double state," where true power lies in the hands of Supreme Leader Khamenei and senior military commanders.
He argued that expanded relations with Washington and the removal of crippling economic sanctions would help moderate figures such as Rouhani engaged in policy and power struggles with Iranian hard-liners. Removal of American embargoes would also help ordinary Iranians who could no longer afford life-saving foreign phamaceuticals, he said.
Saharkhiz's note of cautious optimism was echoed by his son.
"There's a lot of hope from what Rouhani did in the U.S. and there's a lot of good response from the people," Mehdi said. "But then you have a lot of people who were in charge before the election and are still in charge and don't like it."
Son not sure when he can travel to Tehran
For now, Mehdi says it is not safe for him to return to Iran to visit his father. He has yet to fulfill his mandatory Iranian military service, and he fears he could be detained due to his own outspoken criticism of the regime.
"Maybe in a few years I will be able to go back, but it's a really big risk," he said.
Meanwhile, his father predicted he is still at risk of being thrown back in prison.
"I will support freedom in Iran, and maybe criticize the leadership in Iran," he said. "So it is possible that they will come here and capture me again."
Both father and son hope, however, that the authorities will lift an earlier travel ban that prevented the veteran journalist from leaving Iran.
If so, the two hope to reunite for the first time in more than a decade in a third country such as the United Arab Emirates or Turkey.
"It will be a very emotional time," Isa Saharkhiz said.
It would be, his son said, a dream come true.