| 摘要 |
A method and apparatus for improving the security of an electronic codebook encryption scheme comprises a transmitter unit for encoding or encrypting data and a separate authorized receiver for decoding or decrypting the data. During the encryption of the plaintext data, a randomly generated offset is introduced into the PN sequence to vary the starting point of the PN sequence as it is applied to the plaintext data. The offset is encrypted with the secret key and the unencrypted IV, encrypted offset, and ciphertext are exported by the transmitter to the receiver for decrypting. The encoded communication is imported by the receiver and the encrypted offset portion is extracted. The receiver combines the encrypted offset with the secret key to decipher the offset value. The offset and PN sequence are then combined with the ciphertext, using an XOR gate, to recover the original plain text from the ciphertext. In an alternative embodiment, the encoding PN sequence is composed of multiple, non-contiguous random sequence segments comprising a two-dimensional array. An incremental IV ID is generated for each IV issued in the creation of a segment. Each random sequence segment is identifiable by its IV ID. The starting point at which the random sequence segments are applied to a string of plaintext data is deferred from the beginning of the first random sequence segment in accordance with a composite offset.
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