Questions for the 212-81 were updated on : Dec 01 ,2025
Why is quantum computing a threat to RSA?
D
In order to understand RS
B
Which one of the following wireless standards uses AES using the Counter Mode-Cipher Block
Chaining (CBC)-Message Authentication Code (MAC) Protocol (CCMP)?
D
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.
D
John is trying to select the appropriate authentication protocol for his company. Which of the
following types of authentication solutions use tickets to provide access to various resources from a
central location?
A
How does Kerberos generate the first secret key in the authentication process?
B
How many qubits are needed to break RSA?
C
During the process of encryption and decryption, what keys are shared?
A
Explanation:
Public keys
https://en.wikipedia.org/wiki/Public-key_cryptography
Public-key cryptography, or asymmetric cryptography, is a cryptographic system that uses pairs of
keys: public keys, which may be disseminated widely, and private keys, which are known only to the
owner. The generation of such keys depends on cryptographic algorithms based on mathematical
problems to produce one-way functions. Effective security only requires keeping the private key
private; the public key can be openly distributed without compromising security.
In such a system, any person can encrypt a message using the receiver's public key, but that
encrypted message can only be decrypted with the receiver's private key.
Alice and Bob have two keys of their own — just to be clear, that's four keys total. Each party has
their own public key, which they share with the world, and their own private key which they well,
which they keep private, of course but, more than that, which they keep as a closely guarded secret.
The magic of public key cryptography is that a message encrypted with the public key can only be
decrypted with the private key. Alice will encrypt her message with Bob's public key, and even
though Eve knows she used Bob's public key, and even though Eve knows Bob's public key herself,
she is unable to decrypt the message. Only Bob, using his secret key, can decrypt the message
assuming he's kept it secret, of course.
Alice and Bob do not need to plan anything ahead of time to communicate securely: they generate
their public-private key pairs independently, and happily broadcast their public keys to the world at
large. Alice can rest assured that only Bob can decrypt the message she sends because she has
encrypted it with his public key.
You are explaining basic mathematics to beginning cryptography students. You are covering the basic
math used in RS
C
Explanation:
Any number only divisible by one and itself
https://en.wikipedia.org/wiki/Prime_number
A prime number (or a prime) is a natural number greater than 1 that is not a product of two smaller
natural numbers. A natural number greater than 1 that is not prime is called a composite number.
For example, 5 is prime because the only ways of writing it as a product, 1 × 5 or 5 × 1, involve 5
itself. However, 4 is composite because it is a product (2 × 2) in which both numbers are smaller than
4. Primes are central in number theory because of the fundamental theorem of arithmetic: every
natural number greater than 1 is either a prime itself or can be factorized as a product of primes that
is unique up to their order.
In which of the following password protection technique, random strings of characters are added to
the password before calculating their hashes?
C
Explanation:
Salting
https://en.wikipedia.org/wiki/Salt_(cryptography)
A salt is random data that is used as an additional input to a one-way function that hashes data, a
password or passphrase. Salts are used to safeguard passwords in storage. Historically a password
was stored in plaintext on a system, but over time additional safeguards were developed to protect a
user's password against being read from the system.
A new salt is randomly generated for each password. In a typical setting, the salt and the password
(or its version after key stretching) are concatenated and processed with a cryptographic hash
function, and the output hash value (but not the original password) is stored with the salt in a
database. Hashing allows for later authentication without keeping and therefore risking exposure of
the plaintext password in the event that the authentication data store is compromised.
Salts defend against a pre-computed hash attack, e.g. rainbow tables.Since salts do not have to be
memorized by humans they can make the size of the hash table required for a successful attack
prohibitively large without placing a burden on the users. Since salts are different in each case, they
also protect commonly used passwords, or those users who use the same password on several sites,
by making all salted hash instances for the same password different from each other.
Asymmetric encryption method developed in 1984. It is used in PGP implementations and GNU
Privacy Guard Software. Consists of 3 parts: key generator, encryption algorithm, and decryption
algorithm.
D
Explanation:
ElGamal
https://en.wikipedia.org/wiki/ElGamal_encryption
the ElGamal encryption system is an asymmetric key encryption algorithm for public-key
cryptography which is based on the Diffie–Hellman key exchange. It was described by Taher Elgamal
in 1985. ElGamal encryption is used in the free GNU Privacy Guard software, recent versions of PGP,
and other cryptosystems. The Digital Signature Algorithm (DSA) is a variant of the ElGamal signature
scheme, which should not be confused with ElGamal encryption.
Incorrect answers:
Tiger - is a cryptographic hash function designed by Ross Anderson and Eli Biham in 1995 for
efficiency on 64-bit platforms. The size of a Tiger hash value is 192 bits. Truncated versions (known as
Tiger/128 and Tiger/160) can be used for compatibility with protocols assuming a particular hash
size. Unlike the SHA-2 family, no distinguishing initialization values are defined; they are simply
prefixes of the full Tiger/192 hash value.
GOST - hash function, defined in the standards GOST R 34.11-94 and GOST 34.311-95 is a 256-bit
cryptographic hash function. It was initially defined in the Russian national standard GOST R 34.11-94
Information Technology – Cryptographic Information Security – Hash Function. The equivalent
standard used by other member-states of the CIS is GOST 34.311-95.
RIPEMD - is a family of cryptographic hash functions developed in 1992 (the original RIPEMD) and
1996 (other variants). There are five functions in the family: RIPEMD, RIPEMD-128, RIPEMD-160,
RIPEMD-256, and RIPEMD-320, of which RIPEMD-160 is the most common.
What does Output feedback (OFB) do:
C
Explanation:
A block cipher is converted into a stream cipher by generating a keystream blocks, which are then
XORed with the plaintext blocks to get the ciphertext
https://en.wikipedia.org/wiki/Block_cipher_mode_of_operation#Output_feedback_(OFB)
The output feedback (OFB) mode makes a block cipher into a synchronous stream cipher. It generates
keystream blocks, which are then XORed with the plaintext blocks to get the ciphertext. Just as with
other stream ciphers, flipping a bit in the ciphertext produces a flipped bit in the plaintext at the
same location. This property allows many error-correcting codes to function normally even when
applied before encryption.
This algorithm was published by the German engineering firm Seimans in 1993. It is a software based
stream cipher using Lagged Fibonacci generator along with a concept borrowed from the shrinking
generator ciphers.
D
Explanation:
FISH
https://en.wikipedia.org/wiki/FISH_(cipher)
The FISH (FIbonacci SHrinking) stream cipher is a fast software based stream cipher using Lagged
Fibonacci generators, plus a concept from the shrinking generator cipher. It was published by
Siemens in 1993. FISH is quite fast in software and has a huge key length. However, in the same
paper where he proposed Pike, Ross Anderson showed that FISH can be broken with just a few
thousand bits of known plaintext.
Which method of password cracking takes the most time and effort?
C
Explanation:
Brute force
https://en.wikipedia.org/wiki/Brute-force_attack
A brute-force attack consists of an attacker submitting many passwords or passphrases with the hope
of eventually guessing correctly. The attacker systematically checks all possible passwords and
passphrases until the correct one is found. Alternatively, the attacker can attempt to guess the key
which is typically created from the password using a key derivation function. This is known as an
exhaustive key search.
A brute-force attack is a cryptanalytic attack that can, in theory, be used to attempt to decrypt any
encrypted data (except for data encrypted in an information-theoretically secure manner). Such an
attack might be used when it is not possible to take advantage of other weaknesses in an encryption
system (if any exist) that would make the task easier.
Incorrect answers:
Rainbow tables - is a precomputed table for caching the output of cryptographic hash functions,
usually for cracking password hashes. Tables are usually used in recovering a key derivation function
(or credit card numbers, etc.) up to a certain length consisting of a limited set of characters.
Dictionary attack - is a form of brute force attack technique for defeating a cipher or authentication
mechanism by trying to determine its decryption key or passphrase by trying thousands or millions
of likely possibilities, such as words in a dictionary or previously used passwords, often from lists
obtained from past security breaches.
Shoulder surfing - is a type of social engineering technique used to obtain information such as
personal identification numbers (PINs), passwords and other confidential data by looking over the
victim's shoulder, either from keystrokes on a device or sensitive information being spoken and
heard, also known as eavesdropping.
Which of the following is assured by the use of a hash?
D
Explanation:
Integrity
https://en.wikipedia.org/wiki/Cryptographic_hash_function#Verifying_the_integrity_of_messages_
and_files
An important application of secure hashes is verification of message integrity. Comparing message
digests (hash digests over the message) calculated before, and after, transmission can determine
whether any changes have been made to the message or file.