(How does Electronic Codebook (ECB) mode encryption function?

ECB is the simplest block cipher mode: each plaintext block is encrypted independently using the same key and the block cipher primitive. There is no IV and no chaining, so identical plaintext blocks produce identical ciphertext blocks. This property leaks patterns and structure in the plaintext, which is why ECB is generally considered insecure for most real-world data beyond tiny, random-looking inputs. For example, images encrypted with ECB often reveal outlines because repeated pixel blocks map to repeated ciphertext blocks. Option A describes CTR mode, option C describes CBC mode, and option B resembles feedback-based modes. ECB’s independence also means it can be parallelized, but the pattern leakage is a severe weakness. Modern practice prefers authenticated encryption modes (like GCM) or, at minimum, modes with IVs and chaining (like CBC with proper padding and MAC). Therefore, the correct statement is that ECB encrypts each block with the same key and each block is independent of the others.