| 摘要 |
<p>An encryptor/ decryptor capable of achieving secure cryptographic communication by applying appropriate padding to a cryptosystem such as NTRU cryptosystems. When an n-bit plaintext M is received, the OAEP + padding is applied thereto. According to a conversion rule or a conversion function A that satisfies the conditions as described below, two bit strings m and r are obtained from the result of the OAEP + padding. The conversion function A is a map to map a bit string consisting of k bits or less to the element of L m × L r , where L m is the scope of m and L r is the scope of r. The conversion function A should satisfy the following conditions: A is injective; A and the inverse map thereof can be computed by a polynomial time; and if an encryption function is denoted by E(m, r), a map E: A(X) †’ L e is a one-way function, where X is the scope of (m, r) and L e is the space of the entire ciphertext. After a bit string is divided into the two bit strings m and r, e = E r (m) is computed to be encrypted. Thus, a ciphertext e is transmitted to a receiver.</p> |
