Kathy Hilton keeps explicit photos of herself ‘safe in the bank’

Kathy Hilton is opening up about what it takes to have a successful marriage.

The 65-year-old designer and actress recently celebrated 45 years of marriage to her husband, businessman Rick Hilton, and she shared the secret to her long-lasting marriage.

“You have to keep a little mystery,” she told Fox News Digital while hosting the DirecTV Celebrates “Christmas at Kathy’s” event. The annual event is held at Kathy’s home and supports the Ronald McDonald House Charities. Guests are encouraged to donate unwrapped gifts to benefit families living in Ronald McDonald Houses across the nation.

Kathy and Rick first met as teenagers and tied the knot in November 1979. Since getting married, the couple has welcomed four children together — Paris, Nikki, Barron and Conrad.

Kathy Hilton and Rick Hilton then and now split

Kathy’s secret to a successful marriage is to keep the mystery alive. (Getty Images)

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She gave further insight into her marriage on Tuesday night’s episode of “The Real Housewives of Beverly Hills,” which she has been appearing on since its 11th season in May 2011. When asked by her sister, Kyle Richards, if she and Rick have ever texted each other explicit photos, Kathy surprised everyone with her answer.

“We have a couple in the safe in the bank,” Kathy shared, adding she and Rick have never sent each other nude photos via text message. “Caesars Palace in Las Vegas, they have those beds with the big mirror. Seriously, it’s so sexy.”

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In her confessional, Richards reacted to the news, asking herself, “Who puts their nude photos in a vault at the bank?” She added that she was “picturing Kathy naked with, like, fuzzy socks and a hat on.”

Kyle Richards, Kathy Hilton and Kim Richards at the the DIRECTV Celebrates "Christmas at Kathy's" event.

Kathy’s sister, Kyle Richards, was surprised to hear where Kathy keeps her explicit photos. (Gilbert Flores/Variety via Getty Images)

This isn’t the first time Kathy has given fans an inside look at her marriage, telling Page Six in January she and Rick make sure to have dinner together at the Cheesecake Factory once a week.

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“It’s local, it’s right there and fresh and busy all the time,” she explained. “Actually, you walk in there and there are people. We love that. We don’t want to sit in a restaurant with nobody in the room.”