As a novel optoelectronic information material, metasurfaces face a primary scientific challenge: maximizing information capacity while minimizing cost. To address this, this paper proposes a phase modulation method that combines geometric phase and propagation phase using minimalist metasurfaces composed of only two nanostructures. This design achieves holographic decoupling across three wavelength channels, enabling low-crosstalk tri-channel display performance despite limited degrees of freedom. Furthermore, we present a multi-key three-wavelength encryption scheme that integrates conventional image encryption algorithm. This approach significantly enhances information security and reliability. The designed dual-structure metasurfaces offer advantages of simple manufacturing, flexible design capability, and high information storage density, providing new solutions for image display, information encryption, anti-counterfeiting, and high-density optical storage applications.