Cryptographic hashes are often used for message integrity and password storage. It is important to understand the common properties of all cryptographic hashes. What is not true about a hash?
Answer(s): B
Reversible https://en.wikipedia.org/wiki/Hash_functionHash functions are not reversible.Incorrect answers:Fixed length output and Variable length input. Hash function receive variable length input and produce fixed length outputFew collisions. Every hash function with more inputs than outputs will necessarily have collisions
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.
Answer(s): D
Hash https://en.wikipedia.org/wiki/Hash_functionA hash function is any function that can be used to map data of arbitrary size to fixed-size values.
The most widely used asymmetric encryption algorithm is what?
Answer(s): C
RSAThe RSA encryption algorithm is one of the most widely used public key encryption algorithms that have ever been invented. It was created by the three scientists Ronald Rivest, Adi Shamir, and Leonard Adleman in 1977, and today it is increasingly being used in the network area.Incorrect answers:Caesar Cipher - Monoalphabetic cipher where letters are shifted one or more letters in either direction. The method is named after Julius Caesar, who used it in his private correspondence. Vigenere - Multi alphabet cipher Invented by Giovan Battista Bellaso in middle 1553. Vigenere created a stronger version of the cipher. Combining/Weaving Caesar cipher. Not cracked until late 1800s. Widely used from 16th century to early 20th century. It is a cipher square with A to Z across all the columns and rows. You then use a keyword to encrypt the message DES - The Data Encryption Standard is a symmetric-key algorithm for the encryption of digital data.
Which of the following is a fundamental principle of cryptography that holds that the algorithm can be publicly disclosed without damaging security?
Kerkchoff's principle https://en.wikipedia.org/wiki/Kerckhoffs%27s_principleKerckhoffs's principle (also called Kerckhoffs's desideratum, assumption, axiom, doctrine or law) of cryptography was stated by Netherlands born cryptographer Auguste Kerckhoffs in the 19th century:A cryptosystem should be secure even if everything about the system, except the key, is public knowledge.Kerckhoffs's principle was reformulated (or possibly independently formulated) by American mathematician Claude Shannon as "the enemy knows the system", i.e., "one ought to design systems under the assumption that the enemy will immediately gain full familiarity with them". In that form, it is called Shannon's maxim. This concept is widely embraced by cryptographers, in contrast to "security through obscurity", which is not.
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