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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 Mar. 03, 2026 (see below)
An attack that is particularly successful against block ciphers based on substitution-permutation networks. For a block size b, holds b-k bits constant and runs the other k through all 2k possibilities. For k=1, this is just deferential cryptanalysis, but with k>1 it is a new technique.
Integral Cryptanalysis
https://en.wikipedia.org/wiki/Integral_cryptanalysis
Integral cryptanalysis is a cryptanalytic attack that is particularly applicable to block ciphers based on substitution-permutation networks. It was originally designed by Lars Knudsen as a dedicated attack against Square, so it is commonly known as the Square attack. It was also extended to a few other ciphers related to Square: CRYPTON, Rijndael, and SHARK. Stefan Lucks generalized the attack to what he called a saturation attack and used it to attack Twofish, which is not at all similar to Square, having a radically different Feistel network structure. Forms of integral cryptanalysis have since been applied to a variety of ciphers, including Hierocrypt, IDEA, Camellia, Skipjack, MISTY1, MISTY2, SAFER++, KHAZAD, and FOX (now called IDEA NXT).
Incorrect answers:
Chosen Plaintext Attack - is an attack model for cryptanalysis which presumes that the attacker can obtain the ciphertexts for arbitrary plaintexts. The goal of the attack is to gain information that reduces the security of the encryption scheme.
Linear Cryptanalysis - is a general form of cryptanalysis based on finding affine approximations to the action of a cipher. Attacks have been developed for block ciphers and stream ciphers. Linear cryptanalysis is one of the two most widely used attacks on block ciphers.
Differential Cryptanalysis - is a general form of cryptanalysis applicable primarily to block ciphers, but also to stream ciphers and cryptographic hash functions. In the broadest sense, it is the study of how differences in information input can affect the resultant difference at the output. In the case of a block cipher, it refers to a set of techniques for tracing differences through the network of transformation, discovering where the cipher exhibits non-random behavior, and exploiting such properties to recover the secret key (cryptography key).
A _______ product refers to an NSA-endorsed classified or controlled cryptographic item for classified or sensitive U. S. government information, including cryptographic equipment, assembly, or component classified or certified by NSA for encrypting and decrypting classified and sensitive national security information when appropriately keyed
Type 1
https://en.wikipedia.org/wiki/NSA_cryptography#Type_1_Product
A Type 1 Product refers to an NSA endorsed classified or controlled cryptographic item for classified or sensitive U.S. government information, including cryptographic equipment, assembly or component classified or certified by NSA for encrypting and decrypting classified and sensitive national security information when appropriately keyed.
Incorrect answers:
Type 2 - product refers to an NSA endorsed unclassified cryptographic equipment, assemblies or components for sensitive but unclassified U.S. government information.
Type 3 - unclassified cryptographic equipment, assembly, or component used, when appropriately keyed, for encrypting or decrypting unclassified sensitive U.S. Government or commercial information, and to protect systems requiring protection mechanisms consistent with standard commercial practices. A Type 3 Algorithm refers to NIST endorsed algorithms, registered and FIPS published, for sensitive but unclassified U.S. government and commercial information.
Type 4 - Algorithm refers to algorithms that are registered by the NIST but are not FIPS published. Unevaluated commercial cryptographic equipment, assemblies, or components that are neither NSA nor NIST certified for any Government usage.
John is going to use RSA to encrypt a message to Joan. What key should he use?
Joan's public key
https://en.wikipedia.org/wiki/RSA_(cryptosystem)
Suppose Joahn uses Bob's public key to send him an encrypted message. In the message, she can claim to be Alice but Bob has no way of verifying that the message was actually from Alice since anyone can use Bob's public key to send him encrypted messages. In order to verify the origin of a message, RSA can also be used to sign a message.
Suppose Alice wishes to send a signed message to Bob. She can use her own private key to do so. She produces a hash value of the message, raises it to the power of d (modulo n) (as she does when decrypting a message), and attaches it as a 'signature' to the message. When Bob receives the signed message, he uses the same hash algorithm in conjunction with Alice's public key. He raises the signature to the power of e (modulo n) (as he does when encrypting a message), and compares the resulting hash value with the message's actual hash value. If the two agree, he knows that the author of the message was in possession of Alice's private key, and that the message has not been tampered with since.
A _____ is a function that takes a variable-size input m and returns a fixed-size string.
Hash
https://en.wikipedia.org/wiki/Hash_function
A hash function is any function that can be used to map data of arbitrary size to fixed-size values.
Part of understanding cryptography is understanding the cryptographic primitives that go into any crypto system. A(n) _______ is a fixed-size input to a cryptographic primitive that is random or pseudorandom.
Key
https://en.wikipedia.org/wiki/Key_(cryptography)
In cryptography, a key is a piece of information (a parameter) that determines the functional output of a cryptographic algorithm. For encryption algorithms, a key specifies the transformation of plaintext into ciphertext, and vice versa for decryption algorithms. Keys also specify transformations in other cryptographic algorithms, such as digital signature schemes and message authentication codes.
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