Title: Decryption apparatus and decryption method
Application Number: 200510103603 Application Date: 2005.09.07
Publication Number: 1831900 Publication Date: 2006.09.13
Approval Pub. Date: Granted Pub. Date:
International Classifi-cation: G09C1/00
Applicant(s) Name: Toshiba Corp. Address:
Inventor(s) Name:
Attorney & Agent: wang yang
Abstract:
     A decryption apparatus stores secret keys, each of which is specified by two nodes in tree structure in first memory, stores identifier of decryption apparatus corresponding to leaf in tree structure in second memory, acquires ciphertext and ciphertext index information item indicating two nodes, in the tree structure, which correspond to decryption key for decrypting ciphertext, to obtain ciphertexts and ciphertext index information items corresponding to respective ciphertexts, acquires decryptable ciphertext from ciphertexts, one of the two nodes indicated by ciphertext index information item of decryptable ciphertext being ancestor node of leaf and the other of the two nodes being node which is not ancestor node of leaf, selects, from secret keys stored, secret key from which decryption key is derived, derives decryption key from secret key selected, and decrypts decryptable ciphertext by using decryption key derived.
Time: 15