Patent ID: 11876888
Assignee: MITSUBISHI ELECTRIC CORPORATION
Field: Digital communication (Electrical engineering)
Classification: CPC H | IPC H

Claim 12:
13. An encryption method comprising:
acquiring a plaintext M;
dividing the plaintext M every b bits from a beginning, the b bits being a block size of an encryption function E of a block cipher, thereby generating b-bit values M1, . . . , Mm-1 and a value Mm having 1 or more bits to b or less bits;
assigning a b-bit value H1 to a value M0, and for each integer i of i=1, . . . , m in an ascending order, taking a value Mi-1 as input to the encryption function E, thereby calculating a value S1(i), and calculating a value Ci from the value S1(i) and a value Mi;
assigning an r-bit value H2 to a value S2(0), and for each integer i of i=1, . . . , m in an ascending order, calculating a value S2(i) from the value S1(i) and a value S2(i−1);
generating a ciphertext C from a value Ci for each integer i of i=1, . . . , m; and
generating a (b+r)-bit authenticator T by using a value S1(m) and a value S2(m).