SEOUL, South Korea — It is a telling sign of who is the rising star in North Korea: state-run television showing octogenarian party secretaries bowing to a man their grandchildren’s age before accepting the smiling man’s handshake or kowtowing to his instructions.

A year after Kim Jong-un made his public debut as North Korea’s leader-in-waiting, scenes like that — the old party elite groveling — have become a staple of North Korea’s propagandist media, a crucial tool for the country’s leader, Kim Jong-il, to elevate his son as his successor.

“The obvious message of all this to North Koreans is that Kim Jong-un is now dictating to the top elite,” said Cheong Seong-chang, a North Korea specialist at the Sejong Institute in South Korea. “It reflects the regime’s confidence about his status as successor and about another hereditary succession.”

When Kim Jong-un, thought to be in his late 20s, emerged from obscurity a year ago this past week as a four-star general and vice chairman of the Central Military Commission of the Workers’ Party, the first thing the outside world noticed was the obesity he appeared to have inherited from his father and his grandfather, the late Kim Il-sung, the founder of North Korea. (Some South Korean news media outlets speculated that he might have undergone plastic surgery to more closely resemble his grandfather, a godlike figure among North Koreans.)