An encryption key is an algorithm which specifies how a message is to be encoded. The encrypted message is often called ciphertext. The original message is called plain text. See Wikipedia for more information.
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\begin{definition}
An encryption key is an algorithm which specifies how a message is to be encoded. The encrypted message is often called ciphertext. The original message is called plain text. See \href{http://en.wikipedia.org/wiki/Encryption}{Wikipedia} for more information.
\end{definition}
definition ben