Encryption and decryption system and method

An encryption and decryption system is provided, which includes a transmitting device and a receiving device. The transmitting device is used for storing multiple original images and a correspondence table. The receiving device is connected to the transmitting device for storing the correspondence table, wherein the transmitting device generates an encrypted string, the transmitting device selects a representative morphed image from multiple morphed images according to the encrypted string, the transmitting device transmits the representative morphed image to the receiving device, and does not transmit the encrypted string to the receiving device, the receiving device identifies the first original image number and the second original image number from the representative morphed image, and the receiving device looks up the correspondence table according to the first original image number and the second original image number to generate the encrypted string.