A technique used to hide the message within a large amount of useless data.

A technique used to hide the message within a large amount of useless data.

• A. Grille Ciphers
• B. Text Semagrams
• C. Null Ciphers
• D. Image Steganography

Answer: (C)

The idea being tested is hiding a message inside ordinary data by using a simple rule to pick out the real content. That’s a null cipher. The cover text or data looks normal and mostly meaningless, but a hidden message can be extracted by following a pattern or rule—like taking every nth letter, or reading the first letter of each sentence, or selecting certain words at regular intervals. Because the message is concealed only by the way you select data from the surrounding filler, detection requires knowing the rule, not breaking complex cryptography. This contrasts with image steganography, which hides data inside image pixels, and with grille-style methods, which rely on a specific mask to reveal letters from a text. The classic null cipher is precisely about embedding a message in a large amount of seemingly useless data and then pulling it out with the right extraction method.

The idea being tested is hiding a message inside ordinary data by using a simple rule to pick out the real content. That’s a null cipher. The cover text or data looks normal and mostly meaningless, but a hidden message can be extracted by following a pattern or rule—like taking every nth letter, or reading the first letter of each sentence, or selecting certain words at regular intervals. Because the message is concealed only by the way you select data from the surrounding filler, detection requires knowing the rule, not breaking complex cryptography. This contrasts with image steganography, which hides data inside image pixels, and with grille-style methods, which rely on a specific mask to reveal letters from a text. The classic null cipher is precisely about embedding a message in a large amount of seemingly useless data and then pulling it out with the right extraction method.