| 摘要 |
PROBLEM TO BE SOLVED: To resolve the inefficiency in a ciphering using a hash function by using a same pseudo-random function twice. SOLUTION: An inputted 2n bit string is decomposed into n bit strings L and R, an n bit output is generated by a squared hash function, added with a data block L and stored as an n bit strings S (S200 to 208). Thus, an n bit output is generated by a pseudo-random function, added with a data string R and stored as an n bit string T (S210 to 214). Then, an n bit string is generated by the pseudo-random function, which is same as the function of S210, added with the n bit string S and stored as an n bit string V (S216 to 220). Then, n bits are generated by the squared hash function and stored as an n bit string W (S222 to 226). Using the data strings V and W, 2n bit output, which is a ciphered expression, is outputted (S228).
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