[問題] 密碼學 3DES 中間的步驟為何用decryption

[woody3724 (woody)]

密碼學

3DES的加密三個步驟是

E(加密) -> D(解密) -> E(加密)

原文書題到   (以下英文擷取自課本原文書)

There is no cryptographic significance to the use of decryption for the second

stage of 3DES encryption. Its only advantage is that it allows users of 3DES

to decrypt data encrypted by users of the older single DES:

    C = E( K1,D( K1,E( K1, P ) ) ) = E[K,P]

    where C = ciphertext

          P= plaintext

          E[K,X] = encryption of X using key K

          D[K,Y] = decryption of Y using key K

看完這段還是不懂為什麼中間的步驟要用解密

尤其是older single DES不懂

謝謝

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推 suhorng:因為key取一樣就可以變 (1)DES
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