| 摘要 |
The present invention relates to a method and an apparatus for cellular digital telephonic cryptographication including a commutator, when an option between compatibility security and a higher security is required. A simple text is converted into a numerical text, utilizing a three-stage transformation process. In a first stage, the simple text is transformed utilizing a secret code for controlling cryptography by a reversible transformation process. In a second stage, the output of the first stage is transformed by an involution transformation, the code being withdrawn therefrom when the compatibility commutator is in a compatibility arrangement, and entered when said compatibility commutator is in a security arrangement. In a third stage, the output of the second stage is transformed by the inverse of that transformation performed in the first stage. The compatibility commutator has a lower security cryptographication standard and a security cryptographication based on a code.
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