Make the dip: In a small bowl, stir together the mayonnaise and yogurt. (Do not whisk, as the yogurt will thin out.) Stir in the curry, ginger, turmeric, chili powder, paprika, and salt. Cover, and refrigerate for at least 1 hour or overnight.
Preheat the oven to 200°.
Using a large sharp knife, cut the sweet potatoes into strips 3 inches long and 1/8 inch thick. Pat dry with paper towels.
In a deep medium saucepan, heat the oil over high heat until a deep-fry thermometer reads 375°. In batches, deep-fry the sweet potato sticks until golden brown, 3 to 4 minutes. Using kitchen tongs, transfer the sweet potato sticks to a paper towel-lined baking sheet to drain. Keep the sticks warm in the oven while frying the remaining sweet potatoes.
Sprinkle with the salt and pepper, and serve warm, with the curried mayonnaise alongside for dipping.