## Cryptology ePrint Archive: Report 2018/1120

Organizational Cryptography for Access Control

Masahito Gotaishi and Shigeo Tsujii

Abstract: A cryptosystem for granting/rescinding access permission is proposed, based on elliptic curve cryptography. The Organizational Cryptosystem' grants access permission not by giving secret (decription) key to the corresponding user but by converting the ciphertext so that the user can decript with their secret key. The conversion key' for the document, which is created from the secret key which the ciphertext has been originally encrypted for, the public key of the member who shall be permitted to read the ciphertext, and a part of the ciphertext. Therefore it is not possible to decrypt the ciphertext with the conversion key. Nor, for the administrator who issues the conversion key, to obtain any information about the plaintext.

Category / Keywords: public-key cryptography / elliptic curve cryptosystem