| 摘要 |
PROBLEM TO BE SOLVED: To provide a technique capable of decrypting data encrypted in a terminal by a server without exchanging an encryption key between the server and the terminal.SOLUTION: A decryption server 20 includes a database for storing a value generated by applying a different input value to a unidirectional function formed by applying a plurality of initial values to a polynomial with symmetry between the input value and a generated value, the input value, the initial values, and the polynomial in association with each other. A digital broadcasting receiver 10 generates a generation value by providing a different input value to a unidirectional function formed by applying an optional initial value to the polynomial, generates an encrypted data by providing data divided correspondingly to the number of digits of the input value to the unidirectional function and transmits the generated encryption data to the decryption server 20. The decryption server 20 retrieves a polynomial and an initial value respectively overlapped out of polynomials and initial values related to the received plurality of generation values and input values and reads out the retrieved polynomial and initial value and the generation value from the database and decrypts the encrypted data. |
