Substitution, Transposition or Steganography?

About this interactive

Cryptography is the art of concealing information, and the lesson showed three different ways to hide the same word. This activity hands you new examples of each and asks you to name the method. Substitution replaces each letter with a different letter, number or symbol. The Caesar cipher is the classic example: shift the alphabet three places and S becomes V, E becomes H, and SECRET becomes VHFUHW. A key changes how far you shift. With a key of eight, SECRET becomes AMKZMB. The giveaway is that the letters in the ciphertext are not the letters of the message. Transposition keeps every original letter and moves them around. Reverse SECRET and you get TERCES; swap each pair and you get ESRCTE. Count the letters: if the ciphertext uses exactly S, E, C, R, E and T, only their positions changed. Steganography does not scramble the message at all. It hides it inside something that looks ordinary: a photo, a song file, invisible ink between the lines, or a sentence whose first letters spell the word. The point is that nobody looking at the carrier can tell a message is there. That is why the lesson calls it different from cryptography, which changes the message into something unreadable without the key. One question sorts most items: look at what you can see. Different letters means substitution, the same letters in a new order means transposition, and something that looks perfectly normal means steganography.

What you'll learn

Classify a way of concealing a message as substitution, transposition or steganography by asking whether the letters were replaced, moved around, or hidden inside something else
Recognize a shifted alphabet such as the Caesar cipher, with or without a key, as substitution, and a message hidden in an ordinary photo, file or sentence as steganography rather than encryption

Aligned to

ISC2 CC

5.1 Understand data security

CompTIA Security+

1.4 Explain the importance of using appropriate cryptographic solutions.

Cisco CCST Cybersecurity

1.4 Explain encryption methods and applications

Key terms

Substitution: A method of encryption that replaces each element of the plaintext with a corresponding element according to a defined scheme.
Transposition: A method of encryption that rearranges the positions of characters in the plaintext without replacing them.
Steganography: The practice of concealing a message within another medium, such as an image or sentence, so its existence is hidden rather than its content scrambled.
Plaintext: The original, readable message before it has been converted into a hidden or encrypted format.
Ciphertext: The scrambled, unreadable output produced after plaintext has been encrypted using a cipher.
Key: Additional information used in combination with a cipher to encode or decode a secret message.
Cipher: An algorithm used to encrypt and decrypt data.

Topics

Interactive Categorize

About TechKnowSurge

TechKnowSurge builds IT and cybersecurity professionals through hands-on, concept-first training built around real understanding — not memorization. Free interactive tools, structured programs, and 25+ years of real-world experience, all in one place.

Explore free tools and programs →