Which type of encryption is considered to be unbreakable if the stream is truly random and is as large as the
plaintext and never reused in whole or part?

A.
One Time Pad (OTP)

B.
One time Cryptopad (OTC)

C.
Cryptanalysis

D.
Pretty Good Privacy (PGP)

Explanation:
The one-time pad encryption scheme is considered unbreakable only if:
The pad is used only one time.
The pad is as long as the message.
The pad is securely distributed and protected at its destination.
The pad is made up of truly random values.
Incorrect Answers:
B: One time Cryptopad (OTC) is not a valid encryption type.
C: Cryptanalysis refers to the practice of discovering flaws within cryptosystems
D: Pretty Good Privacy (PGP) is a cryptosystem that makes use of cryptographic protection to protect e-mail
and files.

Harris, Shon, All In One CISSP Exam Guide, 6th Edition, McGraw-Hill, 2013, pp. 770-773, 850