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Eccouncil 212-81 Exam Questions
- Topic 1: Information Theory Cryptography Concepts/ Multi-Alphabet Substitution
- Topic 2: Introduction and History of Cryptography/ Breaking the Vigenère Cipher
- Topic 3: Symmetric Cryptography & Hashes/ Single Substitution Weaknesses
- Topic 4: Symmetric Block Cipher Algorithms/ Basic Facts of the Feistel Function
- Topic 5: International Data Encryption Algorithm (IDEA)/ History of Cryptography
- Topic 6: Number Theory and Asymmetric Cryptography/ Advanced Encryption Standard (AES)
- Topic 7: Propagating Cipher-Block Chaining (PCBC)/ Naor-Reingold and Mersenne Twister Pseudorandom Function
- Topic 8: Server-based Certificate Validation Protocol/ Classification of Random Number Generator
- Topic 9: Shiva Password Authentication Protocol (S-PAP)/ Challenge-Handshake Authentication Protocol (CHAP)
- Topic 10: Point-to-Point Tunneling Protocol (PPTP)/ National Security Agency and Cryptography
- Topic 11: Cracking Modern Cryptography: Ciphertext-only and Related-key Attack/ Cracking Modern Cryptography: Chosen Plaintext Attack
- Topic 12: Steganography Implementations/ Example of Symmetric Stream Ciphers: RC4
- Topic 13: Birthday Paradox: Probability/ Mono-Alphabet Substitution
- Topic 14: Cracking Modern Cryptography/ Example of Symmetric Stream Ciphers: PIKE
Free Eccouncil 212-81 Exam Actual Questions
Note: Premium Questions for 212-81 were last updated On Aug. 27, 2026 (see below)
You are explaining the details of the AES algorithm to cryptography students. You are discussing the derivation of the round keys from the shared symmetric key. The portion of AES where round keys are derived from the cipher key using Rijndael's key schedule is called what?
The key expansion phase
https://en.wikipedia.org/wiki/Advanced_Encryption_Standard
KeyExpansion -- round keys are derived from the cipher key using the AES key schedule. AES requires a separate 128-bit round key block for each round plus one more.
Calculates the average LSB and builds a table of frequencies and Pair of Values. Performs a test on the two tables. It measures the theoretical vs. calculated population difference.
Chi-Square Analysis
https://en.wikipedia.org/wiki/Chi-squared_test
A chi-squared test, is a statistical hypothesis test that is valid to perform when the test statistic is chi-squared distributed under the null hypothesis, specifically Pearson's chi-squared test and variants thereof. Pearson's chi-squared test is used to determine whether there is a statistically significant difference between the expected frequencies and the observed frequencies in one or more categories of a contingency table.
In cryptanalysis, the chi-squared test is used to compare the distribution of plaintext and (possibly) decrypted ciphertext. The lowest value of the test means that the decryption was successful with high probability. This method can be generalized for solving modern cryptographic problems.
Incorrect answers:
Raw Quick Pair - statistical analysis on number of unique colors and color number pairs in the picture and you look for least significant bits and manipulation of data in those bits, typically inside of whitespace.
SP network - substitution--permutation network is a series of linked mathematical operations used in block cipher algorithms such as AES (Rijndael), 3-Way, Kalyna, Kuznyechik, PRESENT, SAFER, SHARK, and Square.
Certificate Authority - component of a PKI that creates and maintains digital certificates throughout their life cycles.
A part of understanding symmetric cryptography understands the modes in which it can be used. You are
explaining those modes to a group of cryptography students. The most basic encryption mode is____________.
The message is divided into blocks, and each block is encrypted separately with no modification to the process.
John is trying to explain the basics of cryptography to a group of young, novice, security students. Which one of the following most accurately defines encryption?
Changing a message so it can only be easily read by the intended recipient
https://en.wikipedia.org/wiki/Encryption
Encryption is the process of encoding information. This process converts the original representation of the information, known as plaintext, into an alternative form known as ciphertext. Ideally, only authorized parties can decipher a ciphertext back to plaintext and access the original information. Encryption does not itself prevent interference but denies the intelligible content to a would-be interceptor.
The reverse process from encoding - converting the encoded message back into its plaintext format.
Decoding
Decoding - reverse process from encoding,converting the encoded message back into its plaintext format.
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