Why is AES encryption in ECB mode considered insecure, despite AES itself being secure?

Question

BlackTom AI · Accepted Answer

Question restatement: Why is AES encryption in ECB mode considered insecure, despite AES itself being secure?

Option 1: 'AES-ECB requires keys to be longer than the plaintext message.' This is inaccurate because ECB mode does not impose any requirement that the key length must exceed the plaintext length. AES keys are typically 128, 192, or 256 bits, and these lengths are independent of the size of the plaintext. The mode does not enforce such a constraint, so this statement misstates how ECB operates.

Option 2: 'AES-ECB uses short keys, making brute-force attacks feasible.' This is also incorrect. ECB mode does not inherently use short keys; the security of AES depends on the key length (128/192/256 bits), not on the mode. While shorter keys would be more vulnerable in general, ECB itself does not define or limit key length beyond what AES specifies. The claim confuses the role of the mode with the key size.

Option 3: 'AES-ECB encryption always produces identical ciphertext blocks for identical plaintext blocks.' This is true and the core reason ECB is considered insecure. Because ECB encrypts each 16-byte block independently with the same key, any identical plaintext blocks yield identical ciphertext blocks. This determinism leaks patterns and structure from the plaintext (such as blocks of the same image region encrypting to the same ciphertext), which can enable an adversary to infer information about the data or its contents. The lack of diffusion across blocks is the fundamental flaw here.

Option 4: 'AES-ECB uses XOR operations, which are reversible.' This statement is misleading. While XOR is a reversible operation and is used in some cipher constructions, ECB mode does not hinge on XOR as its core mechanism. ECB simply applies the AES block cipher independently to each block of plaintext; XOR is not the defining feature of ECB's insecurity. This description mischaracterizes how ECB operates and why it leaks patterns.

In summary, the key problem highlighted by the insecure nature of ECB is the deterministic, per-block independence that causes repeated plaintext blocks to produce repeated ciphertext blocks, exposing structural information about the data. The other options incorrectly describe ECB's requirements, key length implications, or the role of XOR in ECB, none of which address the actual security weakness of the mode.

INFO2222 （ND） INFO2222 模拟考试

Why is AES encryption in ECB mode considered insecure, despite AES itself being secure?

View Explanation

Log in for full answers

Similar Questions

Question at position 12 Which mode allows full parallelization for both encryption and decryption?CFB - Cipher Feedback ModeCTR - Counter ModeCBC - Cipher Block ChainingOFB - Output Feedback ModeClear my selection

[7.15] In what mode is the AES256 algorithm used for encrypted backups?

In a consumer society, many adults channel creativity into buying things

Economic stress and unpredictable times have resulted in a booming industry for self-help products

People born without creativity never can develop it

A product has a selling price of $20, a contribution margin ratio of 40% and fixed cost of $120,000. To make a profit of $30,000. The number of units that must be sold is: Type the number without $ and a comma. Eg: 20000

Which of the following statement regarding cost is correct:

Under the assumptions used in cost-volume-profit analysis, as the activity increases:

More Practical Tools for Students Powered by AI Study Helper

Homework AI Solver

Stylized AI Paper Writer

Plagiarism Checker Assistant

Citation AI Academic Writing Tool

In-Class Translation Assistant

AI Note Generator

AI Quiz Answers

Past Exam Questions from University Test Bank

Smart Practice Assistant

Adaptive Practice

Making Your Study Simpler