| 摘要 |
ELT transformation circuits 1011 to 101m are preliminarily supplied with ELT transformation parameters ai, bi, and pi (i=1, 2, . . . , m). When a plaintext of n bits long is supplied to the ELT transformation circuit 1011 via an input terminal 104, the ELT transformation circuit 1011 carries out ELT transformation on the plaintext by the use of ELT transformation parameters a1, b1, and p1 supplied from an input terminal 1051. An enciphering circuit 1021 enciphers an n/2-bit input with reference to a cryptographic key K1 from an input terminal 1061. Supplied with two n-bit inputs, an exclusive-OR circuit 1031 carries out an exclusive-OR operation between every corresponding bits of the same order. Subsequently, similar operation as mentioned above is repeated. The ELT transformation circuit 101m at a final stage delivers a ciphertext to an output terminal 107.
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