Which property hides the relationship between the key and ciphertext?

• A. Diffusion
• B. Confusion
• C. Padding
• D. ECB Mode

Answer: (B)

Confusion is the property that hides the relationship between the key and the ciphertext. It makes the key’s influence on the output highly nonlinear and complex so small changes in the key produce unpredictable changes in the ciphertext, preventing someone from deducing the key by analyzing the encrypted data. This is typically achieved through nonlinear substitutions and key-dependent transformations that scramble how the key affects each bit or block of ciphertext.

Diffusion, in contrast, spreads the influence of a single plaintext bit across many ciphertext bits to hide patterns in the plaintext itself, not to conceal how the key maps to the ciphertext. Padding is about aligning the message length to a block size, not about confusing the key–ciphertext link. ECB mode describes how blocks are encrypted but doesn’t in itself address hiding the key’s relationship to the ciphertext.