Correct Answer: A
Explanation/Reference:
Explanation:
This question is asking what the opposite of plain text is. In the context of information security, plain text means unencrypted text. The opposite of plain text is cipher text. Cipher text is another term for encrypted text.
Encryption is a method of transforming readable data, called plaintext, into a form that appears to be random and unreadable, which is called ciphertext. Plaintext is in a form that can be understood either by a person (a document) or by a computer (executable code). Once it is transformed into ciphertext, neither human nor machine can properly process it until it is decrypted. This enables the transmission of confidential information over insecure channels without unauthorized disclosure.
Incorrect Answers:
B: This answer is close but incorrect. Plaintext is readable data. The opposite of that is encrypted data (known as ciphertext), not 'encryption'.
C: Unplain text is not a valid term.
D: Digitally Signed is not the opposite of plaintext.
References:
Harris, Shon, All In One CISSP Exam Guide, 6th Edition, McGraw-Hill, 2013, p. 765