"It won't necessarily be a short engagement. They haven't begun planning the wedding yet," a source said.Ashton reportedly wanted to keep things simple when it came to choosing the perfect ring.A source added, "It's a simple band with a round diamond. No baguettes, no insets. It's not ostentatious, like a Kim Kardashian ring. She doesn't need a security team with her to wear it. It's a lot like her and Ashton."