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Suppose that Alice wants to send some secret messages to Bob

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Suppose that Alice wants to send some secret messages to Bob. They agree to solve the problem of sharing a secret key by using as their shared secret key the first paragraph in the first chapter from the book of "Cryptography and Network Security" by W. Stallings that they both have. Here is the paragraph (refer to your text for a complete one) and a ciphertext produced with the key.
1st Paragraph:
The requirements of information security within an organization have undergone ... An example of the latter is personnel screening procedures used during the hiring process.
The Ciphertext:
WQZVYCV TDDQAWDNCI DY UNCR T AYDNLQ NC DMNV CTZZTDNLQ BNFF HQ WZYVQEJDQR; WQZVYCV TDDQAWDNCI DY UNCR T AYZTF NC ND BNFF HQ HTCNVMQR; WQZVYCV TDDQAWDNCI DY UNCR T WFYD NC ND BNFF HQ VMYD.
Decrypt the ciphertext and recover the plaintext. Explain the steps you used to derive the key and the original plaintext. (Hint: a simple substitution cipher used)