WGU Course C839 - Intro to Cryptography Questions Correctly Answered 2023 GRADED A

WGU Course C839 - Intro to Cryptography Questions Correctly Answered 2023 GRADED A What type of encryption uses different keys to encrypt and decrypt the message? A Symmetric B Private key C Secure D Asymmetric - Answer D The most widely used asymmetric encryption algorithm is what? A RSA B Vigenere C DES D Caesar Cipher - Answer A Original, unencrypted information is referred to as ____. A text B plaintext C cleantext D ciphertext - Answer B Which of the following is NOT an asymmetric system? A PGP B RSA C SSL D DES - Answer D In order for User A to send User B an encrypted message that only User B can read, User A must encrypt message with which of the following keys? A User A's public key B User A's private key C User B's public key D User B's private key - Answer C The greatest weakness with symmetric algorithms is _____. A They are less secure than asymmetric B The problem of key exchange C They are slower than asymmetric D The problem of generating keys - Answer B Which of the following is generally true about block sizes? A Smaller block sizes increase security B Block sizes must be more than 256 bits to be secure C Block size is irrelevant to security D Larger block sizes increase security - Answer D A _____ is a function that takes a variable-size input m and returns a fixed-size string. A Symmetric cipher B Hash C Asymmetric cipher D Feistel - Answer B Which of the following is a cryptographic protocol that allows two parties to establish a shared key over an insecure channel? A Elliptic Curve B RSA C MD5 D Diffie-Hellman - Answer D A _________ is a digital representation of information that identifies you as a relevant entity by a trusted third party? A Digital Signature B Hash C Ownership stamp D Digest - Answer A What is the standard used by most digital certificates? A X.509 B CRL C RFC 2298 D OCSP - Answer A DES uses keys of what size? A 56 bits B 192 bits C 128 bits D 64 bits - Answer A Which of the following is NOT a key size used by AES? A 512 bits B 128 bits C 192 bits D 256 bits - Answer A Which of the following was a multi alphabet cipher widely used from the 16th century (1553) to the early 20th century (1900s)? A Vigenere B Caesar C Atbash D Scytale - Answer A Which of the following is a substitution cipher used by ancient Hebrew scholars? A Caesar B Vigenere C Scytale D Atbash - Answer D Shifting each letter in the alphabet a fixed number of spaces to the right or left is an example of what? A Bit shifting B Confusion C Multi substitution D Single substitution - Answer D Which of the following most accurately defines encryption? A changing a message so it can only be easily read by the intended recipient B Making binary changes to a message to conceal it C changing a message using complex mathematics D Applying keys to plain text - Answer A If you use substitution alone, what weakness is present in the resulting cipher text? A It is the same length as the original text B It is easily broken with modern computers. C It is too simple. D Because it maintains letter and word frequency. - Answer D _____ uses at least two different shifts, changing the shift with different letters in the plain text. A Atbash B multi-alphabet encryption C Scytale D Caesar cipher - Answer B ____ was designed to provide built in cryptography for the clipper chip. A Blowfish B Skipjack C GOST D 3DES - Answer B Which of the following uses an 80 bit key on 64 bit blocks? A Twofish B AES C Skipjack D DES - Answer C With _____, the message is divided into blocks and each block is encrypted separately. This is the most basic mode for symmetric encryption. A Electronic codebook (ECB) B Cipher-block chaining (CBC) C Cipher feedback (CFB) D Output feedback (OFB) - Answer A Which of the following is an example of an unbalanced Feistel? A 3DES B Skipjack C Twofish D AES - Answer B This process is done by having each block of plaintext is XORed with the previous ciphertext block before being encrypted. A Output feedback (OFB) B Cipher-block chaining (CBC) C Electronic codebook (ECB) D Cipher feedback (CFB) - Answer B The process wherein the ciphertext block is encrypted then the ciphertext produced is XOR'd back with the plaintext to produce the current ciphertext block is called what? A Output feedback (OFB) B Cipher-block chaining (CBC) C Cipher feedback (CFB) D Electronic codebook (ECB) - Answer C This is a method for turning a block cipher into a stream cipher by generating a keystream block, which are then XORed with the plaintext blocks to get the ciphertext. A Cipher feedback (CFB) B Electronic codebook (ECB) C Output feedback (OFB) D Cipher-block chaining (CBC) - Answer C Which of the following modes can be used to turn a block cipher into a stream cipher? A Propagating cipher-block chaining (PCBC) and Electronic codebook (ECB) B Counter Mode (CTR) and Propagating cipher-block chaining (PCBC) C Electronic codebook (ECB) and Output feedback (OFB) D Output feedback (OFB) and Counter Mode (CTR) - Answer D A fixed-size pseudorandom number that is fed into a symmetric cipher to increase randomness is called what? A IV B Key C Chain D Salt - Answer A A number that is used only one time then discarded is called what? A Nonce B Chain C Salt D IV - Answer A Which of the following is a stream cipher that uses variable length key from 1 to 256 bytes? A RC4 B AES C DESx D DES - Answer A 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. A RC4 B Blowfish C FISH D Twofish - Answer C Which of the following is NOT required for a hash? A Minimum key length of 256 bits B Variable-length input, fixed-length output C Non-reversible D Few collisions - Answer A A ______ refers to a situation where two different inputs yield the same output. A Substitution B Convergence C Collision D Transposition - Answer C What is a salt? A Key rotation B Random bits intermixed with a hash to increase randomness and reduce collisions. C Random bits intermixed with a symmetric cipher to increase randomness and make it more secure. D Key whitening - Answer B RFC 1321 describes what hash? A RIPEMD B SHA1 C GOST D MD5 - Answer D What size block does FORK256 use? A 256 B 128 C 512 D 64 - Answer C In 1977 researchers at MIT described what asymmetric algorithm? A RSA B AES C DH D EC - Answer A What is the formula (M^e)(%n) related to? A Encrypting with EC B Generating Mersenne primes C Decrypting with RSA D Encrypting with RSA - Answer C Which of the following equations is related to EC? A P = Cd%n B Me%n C y2 = x3 + Ax + B D Let m = (p-1)(q-1) - Answer C U.S. Patent 5,231,668 and FIPS 186 define what algorithm? A AES B RSA C Elliptic Curve (EC) D Digital Signature Algorithm (DSA) - Answer D What is X.509? A The standard for PGP certificates B The standard for encrypting email C The standard for FIPS 186 D The standard for digital certificates - Answer D What is contained in a CRL? A Keys for RSA B New certificates C Revoked certificates D Keys for AES - Answer C What does the Online Certificate Status Protocol (OCSP) provide? A Revoked certificates B Hashing C VPN connectivity D Encryption - Answer A In terms of cryptanalysis, what does it mean to break a cipher? A finding a method to decrypt a message that is at least twice as efficient as brute force B trying every possible key until you can decrypt the message C deploying an algorithm that uses a 228 bit key D finding any method to decrypt the message that is more efficient than brute force - Answer D An authentication method that periodically re-authenticates the client by establishing a hash that is then resent from the client is called ______. A PAP B CHAP C SPAP D EAP - Answer B What is a TGS? A The server that grants Kerberos tickets B protocol for encryption C protocol for key exchange D The server that escrows keys - Answer A What is Kerchoff's principle? A A minimum key size of 256 bits is necessary for security. B Both algorithm and key should be kept secret. C A minimum of 15 rounds is needed for a Feistel cipher to be secure. D Only the key needs to be secret, not the actual algorithm. - Answer D Which of the following is a fundamental principle of cryptography that holds that the algorithm can be publically disclosed without damaging security? A Babbage's principle B Kerkchoff's principle C Vigenere's principle D Shamir's principle - Answer B A process that puts a message into the least significant bits of a binary file is called what? A Symmetric cryptography B Masking C Steganography D Asymmetric cryptography - Answer C If you wished to see a list of revoked certificates from a CA, where would you look? A CRL B CA C RFC D RA - Answer A Which of the following is generally true about block ciphers? A Secret block ciphers should be trusted. B Block ciphers permute the bits of the input plaintext. C The plaintext and ciphertext are always the same size. D A block cipher is an encryption function for variable-size blocks of data. - Answer C What does the OCSP protocol provide? A encryption B VPN connectivity C hashing D a real time protocol for verifying certificates - Answer D U.S. encryption standard that replaced DES. Block symmetric cipher that uses 128- bit block sizes and various key lengths (128, 192, 256). - Answer AES DES, 3DES, SHA, AES (some AES implementations are Type I) - Answer Class 3 Algorithms Encryption method where the sender and receiver use an instance of the same key for encryption and decryption purposes. - Answer Symmetric Block symmetric algorithm chosen by NIST as an encryption standard in 1976. It uses a 56-bit true key bit size, 64-bit block size, and 16 rounds of computation. - Answer Data Encryption Standard (DES) technical specification indicating how multimedia data and e-mail binary attachments are to be transferred. - Answer Multipurpose Internet Mail Extensions (MIME) Valid data transmission is maliciously or fraudulently repeated to allow an entity gain unauthorized access. - Answer Replay Attack protocol suite provides a method of setting up a secure channel for protected data exchange between two devices. - Answer Internet Protocol Security (IPSec) Juniper (block cipher) MAYFLY (asymmetric) FASTHASH (hashing) WALBURN (high bandwith link encryption) PEGASUS (satellite telemetry) - Answer Class 1 Algorithms Component of a PKI that creates and maintains digital certificates throughout their life cycles. - Answer Certificate Authority Uses public key encryption and provides data encryption, server authentication, message integrity, and optional client authentication. It is currently at version 3.0. - Answer Secure Sockets Layer (SSL) Manipulating individuals so that they will divulge confidential information, rather than by breaking in or using technical cracking techniques. - Answer Social engineering attack Cryptanalysis attack where the attacker is assumed to have access only to a set of ciphertexts. - Answer Ciphertext-only attack servers and software signing, for which independent verification and checking of identity and authority is done by issuing CA - Answer Class 3 Certificates it should be impossible for any attacker to calculate, or otherwise guess, from any given subsequence, any previous or future values in the sequence - Answer BSI Criteria K3 states Cryptanalysis attack that uses identified statistical patterns. - Answer Statistical attack organizations for which proof of identity is required - Answer Class 2 Certificates Block symmetric cipher that uses a 128-bit key and 64-bit block size. - Answer International Data Encryption Algorithm (IDEA) individuals, and intended for email - Answer Class 1 Certificates A form of cryptanalysis applicable to symmetric key algorithms that was invented by Eli Biham and Adi Shamir. The examination of differences in an input and how that affects the resultant difference in the output. - Answer Differential cryptanalysis Cryptanalysis attack where the attacker is assumed to have access to sets of corresponding plaintext and ciphertext. - Answer Known plaintext attack Carries out real-time validation of a certificate and reports back to the user whether the certificate is valid, invalid, or unknown. OCSP checks the CRL that is maintained by the CA. - Answer Online Certificate Status Protocol (OCSP) What is the formula Me%n related to? - Answer Encrypting with RSA Plain-text is equal to the encryption function (E) with the key (k) and the ciphertext (c) being passed as parameters to that function - Answer P= E(k,c) Symmetric decryption Not certified for government use - Answer Class 4 algorithms 64 bit algorithm operating at 56 bits with an 8 bit parity block - Answer DES AH is the authenticating protocol, and ESP is an authenticating and encrypting protocol that uses cryptographic mechanisms to provide source authentication, confidentiality, and message integrity. - Answer Authentication Header (AH) and Encapsulating Security Payload (ESP). developed as a Russian national standard and produced fixed length outputs of 256 bits - Answer GOST A measure of the uncertainty associated with a random variable - Answer Entropy Attempts to make the statistical frequencies of the ciphertext and actual key as complex as possible - Answer Confusion Like AES, Serpent has a block size of 128 bits and can have a key size of 128, 192, or 256 bits. The algorithm is also a substitution-permutation network like AES. It uses 32 rounds working with a block of four 32-bit words. Each round applies one of eight 4-bit to 4-bit S-boxes 32 times in parallel. Designed by Ross Anderson, Eli Biham, and Lars Knudsen. - Answer Serpent What is the difference between Secure HTTP (SHTTP) and HTTP Secure (HTTPS)? - Answer S-HTTP is a technology that protects each message sent between two computers, while HTTPS protects the communication channel between two computers, messages and all. Which of the following was a multi alphabet cipher widely used from the 16th century to the early 20th century? - Answer Vigenere A _____ is a function that takes a variable-size input m and returns a fixed-size string. - Answer Hash A small change that yields large effects in the output. - Answer Avalanche Private organizations or governmental security - Answer Class 5 Certificates Numbers that have no factors in common with another. - Answer Co-prime numbers Cryptanalysis attack that exploits vulnerabilities within the intrinsic algebraic structure of mathematical functions. - Answer Algebraic attack Designed by Ross Anderson and Eli Biham in 1995. The size of a ________ hash value is 192 bits. - Answer TIGER In order for User A to send User B an encrypted message that only User B can read, User A must encrypt message with which of the following keys? - Answer User B's public key Public key algorithm that can be used for digital signatures, encryption, and key exchange. an extension of the Diffie-Hellman algorithm. - Answer El Gamal Block symmetric cipher that was chosen to fulfill the Advanced Encryption Standard. It uses a 128-bit block size and various key lengths (128, 192, 256). - Answer Rijndael Published by Siemens in 1993. A software-based stream cipher using a Lagged Fibonacci generator (pseudorandom number generator). - Answer FISH 128 bit hash. RFC 1321 - Answer MD5 Cipher text (C) is equal to the encryption function (E) with the key (k) and plain-text (p) being passed as parameters to that function - Answer C = E(k,p) Symmetric encryption It is impossible to compress the data such that the code is less than the Shannon entropy of the source, without it being virtually certain that information will be lost - Answer Shannon's source coding theorem A non-secret binary vector used as the initializing input algorithm for the encryption of a plaintext block sequence to increase security by introducing additional cryptographic variance. - Answer IV (Initialization Vector) If a cryptanalysis uncovers a method that can derive a key for an algorithm, but is only slightly faster than brute force, what is this called? - Answer Success • Confidentiality • Access control • Integrity • Authentication • Nonrepudiation - Answer PKI services It should be impossible for any attacker to calculate, or guess from an inner state of the generator, any previous numbers in the sequence or any previous inner generator states - Answer BSI criteria K4 states: Developed by the NSA for use in the clipper chip. Skipjack uses an 80-bit key to encrypt or decrypt 64-bit data blocks. It is an unbalanced Feistel network with 32 rounds. - Answer Skipjack Algorithm that was chosen for the Data Encryption Standard, which was altered and renamed Data Encryption Algorithm. - Answer Lucifer Announced by NIST as FIPS 197. Has 3 key sizes: 128, 192, 256 and all operate on 128 bit block - Answer AES Symmetric cipher that applies DES three times to each block of data during the encryption process. - Answer Triple DES (3DES) Attack that uses information (timing, power consumption) that has been gathered to uncover sensitive data or processing functions. - Answer Side-channel attack A 160 bit hash with 3 other versions: RIPEMD-128 (128 bit), RIPEMD-256 (256 bit), RIPEMD-320 (320 bit) - Answer RIPEMD-160 Transposition processes used in encryption functions to increase randomness. - Answer Diffusion Used to store, distribute, and maintain cryptographic session and secret keys. - Answer Key Distribution Center (KDC) Designed by Phil Zimmerman as a freeware e-mail security program and was released in 1991. It was the first widespread public key encryption program. - Answer Pretty Good Privacy (PGP) A number that is used only one time then discarded is called what? - Answer Nonce Improvement on FISH due to vulnerability to known-plaintext attacks. Published by Ross Anderson. - Answer PIKE Stands for Menezes-Qu-Vanstone and is a protocol used for key agreement that is based on DH. Incorporated in public key standard IEEE P1363 - Answer MQV A cryptographic protocol and infrastructure developed to send encrypted credit card numbers over the Internet. - Answer Secure Electronic Transaction (SET) The algorithm is used identically for encryption and decryption as the data stream is simply XORed with the key. RC4 uses a variable-length key from 1 to 2048 bits, (minimum of 40 bits or higher to be considered secure). That key constitutes a state table that is used for the subsequent generation of pseudo-random bytes and then to generate - Answer RC4 The payload and the routing and header information are protected in this mode. - Answer Tunnel mode Values that are used with algorithms to increase randomness for cryptographic functions. - Answer Initialization vectors (IVs) Ticket granting service - Answer TGS This is a variation of DES that XORs another 64-bit key to the plaintext before applying the DES algorithm. The concept of simply XORing in an additional key is called whitening. This adds to the confusion of the resultant text. - Answer DESx The total number of co prime numbers for a number n - Answer Euler's Totient Naor-Reingold, Mersenne Twister, Linear Congruential Generator, Lehmer Random Number Generator (twisted generalized feedback shift registers), Lagged Fibonacci Generator (LFG) - Answer Examples of PRNGs (pseudo random number generators) Skipjack, Key Exchange Algorithm (KEA) - Answer Class 2 Algorithms Responsible for the accuracy of the information contained in a certificate request. The _______________ is a proxy for the CA and also expected to perform user validation before issuing a certificate request. - Answer Registration authority (RA) HTTP running over SSL. - Answer HTTP Secure (HTTPS) Component that keeps track of the different SAs and tells the device which one is appropriate to invoke for the different packets it receives. - Answer security parameter index (SPI) Which encryption standard is used primarily for mobile devices? - Answer ECC Stream symmetric cipher that was created by Ron Rivest of RSA. Used in SSL and WEP. - Answer RC4 256 bit and 512 bit hash - Answer SHA-2 Microchip installed on the motherboard of modern computers and is dedicated to carrying out security functions that involve the storage and processing of symmetric and asymmetric keys, hashes, and digital certificates. - Answer Trusted Platform Module (TPM) Cryptographic hash function that uses a symmetric key value and is used for data integrity and data origin authentication. - Answer Hashed message authentication code (HMAC) Type of tunneling mechanism that provides terminal-like access to remote computers. Provides authentication and secure transmission over vulnerable channels like the Internet. - Answer Secure Shell (SSH) Is an authentication key agreement cryptography function very similar to DiffieHellman. - Answer MQV (Menezes-Qu-Vanstone) Provide authentication of a sender and integrity of a sender's message. A message is input into a hash function. Then the hash value is encrypted using the private key of the sender. The result of these two steps yields a __________________. - Answer Digital Signature A 16-round Feistel cipher working on 64-bit blocks. Unlike DES, it can have varying key sizes ranging from 32 bits to 448 bits. Designed by Bruce Schneier. - Answer Blowfish Which of the following modes can be used to turn a block cipher into a stream cipher? - Answer Output feedback (OFB) and Counter Mode (CTR) Online business transactions between companies - Answer Class 4 certificates EFS is encryption for files while Bitlocker is used for full disk encryption - Answer EFS vs. Bitlocker Cryptanalysis attack that exploits vulnerabilities within the algorithm structure. - Answer Analytic attack Open-community and standardized version of SSL but TLS is more extensible and is backward compatible with SSL. - Answer Transport-Layer Security (TLS) Uses a block size of 128 bits and key sizes up to 256 bits. It is a Feistel cipher. Designed by Bruce Schneier, John Kelsey, Doug Whiting, David Wagner, Chris Hall, and Niels Ferguson. - Answer Twofish 160 bit hash - Answer SHA-1 Cryptographic attack that exploits the mathematics behind the birthday problem in the probability theory forces collisions within hashing functions. - Answer Birthday attack A process that puts a message into the least significant bits of a binary file is called what? - Answer Steganography Cryptanalysis attack that tries to uncover a mathematical problem from two different ends. - Answer Meet-in-the-middle attack 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. - Answer El Gamal A combination of the ISAKMP and OAKLEY protocols. - Answer Internet Key Exchange (IKE) The payload of the message is protected - Answer Transport mode What did WPA replace RC4 with? - Answer TKIP (Temporal Key Integrity Protocol) N denotes natural numbers. These are also sometimes called the counting numbers. They are 1, 2, 3, etc. Z denotes the integers. These are whole numbers such as -1, 0, 1, 2, etc. Basically, this set is the natural numbers combined with zero and the negative numbers. Q denotes rational numbers (or the ratios of integers). They are any number that can be expressed as a ratio of two integers. Examples are 3/2, 17/4, and 1/5. R denotes real numbers. This includes the rational number as well as numbers that cannot be expressed as a ratio of two integers, such as 2/3. i denotes imaginary numbers. These are numbers whose square is a negative. For example, √-1 = 1i. - Answer Explain the number groupings: N, Z, Q, R, i An encryption function for fixed-size blocks of data. The current generation has a block size of 128 bits (16 bytes). - Answer block cipher To encrypt with a block cipher, we need a ___________. - Answer secret key Don't ever trust a ____________ or ________________. (Kerckhoffs's Principle) - Answer secret block cipher; secret algorithm A protocol for online shopping with a credit card. One of its features is that it encrypts the credit card number so that an eavesdropper cannot copy it. - Answer SET _______________ is the worst enemy of security, and it almost always comes in the form of features or options. - Answer Complexity ______________ is a measure of how many things interact at any one point. If the effect of an option is limited to a small part of the program, then it cannot interact with an option whose effect is limited to another part of the program. - Answer Complexity The original message, m is called the ______________. - Answer plaintext The public-key algorithms are used to establish _________, which in turn is used to encrypt the actual data. This combines the flexibility of public-key cryptography with the efficiency of symmetric-key cryptography. - Answer a secret key Digital signatures are the public-key equivalent of ______________________. - Answer message authentication codes For practical reasons, a PKI is often set up with multiple levels of CAs. There is a top-level CA, called the ________, which issues certificates on the keys of lowerlevel CAs, which in turn certify the user keys. - Answer root A ____________________ is what most people mean when talking about breaking an encryption system. This is the situation in which Alice and Bob are encrypting their data, and all you as the attacker get to see is the ciphertext. Trying to decrypt a message if you only know the ciphertext is called a ciphertext-only attack. This is the most difficult type of attack, because you have the least amount of information. - Answer ciphertext-only attack A ________________ is one in which you know both the plaintext and the ciphertext. The most obvious goal is to find the decryption key. - Answer known-plaintext attack A known-plaintext attack is more powerful than a ciphertext-only attack. A True B False - Answer A A __________________ is any nontrivial method that detects a difference between the ideal encryption scheme and the actual one. This covers all the attacks we have discussed so far, as well as any yet-to-be-discovered attacks. - Answer distinguishing attack A ____________________is an attack that depends on the fact that duplicate values, also called collisions, appear much faster than you would expect. - Answer Birthday attack An __________________ attack is one that tries all possible values for some target object, like the key. If an attack requires 2^235 steps of work, then this corresponds to an exhaustive search for a 235-bit value. - Answer exhaustive search First introduced by Eli Biham in 1993, a ___________ attack assumes that the attacker has access to several encryption functions. These functions all have an unknown key, but their keys have a relationship that the attacker knows. - Answer related-key A _____________ cipher is one for which no attack exists. - Answer secure block An attack on a block cipher is a non-generic method of distinguishing the block cipher from an ______________ cipher. - Answer ideal block Most modern block ciphers have a ________ block size, but they operate on 32-bit words. - Answer 128-bit An _____________ cipher implements an independently chosen random even permutation for each of the key values. - Answer ideal block The simplest method to encrypt a longer plaintext is known as the _______________________. It has serious weakness, therefore, do not use this method. - Answer electronic codebook mode (ECB) _____________________ was a cylinder tool used by the Greeks, and is often specifically attributed to the Spartans. It was a physical cylinder that was used to encrypt messages. Turning the cylinder produced different ciphertexts. While it is not clear exactly how old this cipher is, it was first mentioned in the 7th century BC by the Greek poet Archilochus. The recipient uses a rod of the same diameter as the one used to create the message. He then wraps the parchment to read the message. To encrypt, one simply writes across the leather. - Answer Scytale Caesar Cipher - Every letter is shifted a fixed number of spaces to the left or the right in the alphabet. The reason it is easy to crack is the issue of letter and word frequency. Atbash Cipher - is a Hebrew code, easier to crack than Caesar, which substitutes the first letter of the alphabet for the last and the second letter for the second to the last, etc. It simply reverses the alphabet Used by Hebrew scribes copying the book of Jeremiah. Example: A becomes Z, B becomes Y, C becomes X, etc. Affine Cipher - is any single-substitution alphabet cipher (also called mono-alphabet substitution) in which each letter in the alphabet is mapped to some numeric value, permuted with some relatively simple mathematical function, and then converted back to a letter. The formula for Affine is: ax + b (mod M). M=26, x=Plaintext numerical equivalent, b=the shift, a=some multiple. For Caesar a=1. Rot13 Cipher - is another single alphabet substitution cipher. It is, in fact, the simplest of all of them. It is really just a permutation of the Caesar cipher. All characters are rotated 13 characters through the alphabet. - Answer Examples of Mono-Alphabet Substitution Homophonic substitution was one of the earlier attempts to make substitution ciphers more robust by_________ the letter frequencies. - Answer masking In World War II, the Germans used this as an electromechanical rotor-based cipher system. The machine was designed so that when the operator pressed a key, the encrypted ciphertext for that plaintext was altered each time. So, if the operator pressed the A key, he or she might generate an F in the ciphertext, and the next time, it might be a D. Essentially, this was a multi-alphabet cipher consisting of 26 possible alphabets. - Answer The Enigma Machine Cipher Disk - The cipher disk, like Scytale, is a physical device used to encrypt. The cipher disk was invented by Leon Alberti in 1466. The cipher disk was polyalphabetic; each time you turned the disk, you used a new cipher. It was literally a disk you turned to encrypt plaintext. Vigenère Cipher - is perhaps the most widely known multi-alphabet substitution cipher. At one time, multi-alphabet substitution was considered quite secure. In fact, the Vigenère cipher was used in the 1800s and early 1900s. The Vigenère cipher was invented in 1553 by Giovan Battista Bellaso. It is a method of encrypting alphabetic text by using a series of different Caesar ciphers based on the letters of a keyword. This is a very effective multi-alphabet cipher and prior to the advent of computers was considered quite strong. It should be noted that the longer the keyword, the more alphabets used to encrypt the message, and thus the stronger the encryption. In fact, one does not even need to use a real word. Any series of letters will work. In 1863, Friedrich Kasiski was the first person to publish a successful general attack on the Vigenère cipher. Playfair Cipher - invented in 1854 by Charles Wheatstone. It was named after Lord Playfair who promoted the use of the cipher. uses a five-by-five table containing a keyword or key phrase. To generate the key table, one would first fill in the spaces in the table with the letters of the keyword (dropping any duplicate letters), then fill the remaining spaces with the rest of the letters of the alphabet in order. People often omitted Q from the list. To encrypt a message, you would break the message into groups of two letters. For example, "CheeseBurger" becomes "Ch ee se Bu rg er", and then you would be map out on the key table. If both letters are the same (or only one letter is left), add an "X" after the first letter. Encrypt the new pair and continue. If the letters appear on the same row of your table, replace them with the letters to their immediate right. If the letters appear on the same column of your table, replace them with the letters immediately below. ADFGVX Cipher - This was the first cipher used by the German Army during World War I. It was invented by Colonel Fritz Nebel in 1918. This was a transposition cipher which used a modified Polybius square with a single columnar transposition used to encode a 36-letter alphabet. This was actually an extension of an earlier cipher called ADFGX. The key for this algorithm is a six-by-six square of letters. This is known as a Polybius square. It is comprised of the letters of the alphabet and the numbers 0 through 9 distributed randomly in the square. The letters A, D, F, G, V, and X are used as coordinates for the square. - Answer Examples of poly-alphabetic substitution _________ allows you to enter in any text, choose the historic algorithm you wish to use, then encrypt that text in a matter of seconds. - Answer CrypTool Many experts believe that modern cryptography begins with _____________________ In 1949 he published a paper in the in the Bell System Technical Journal entitled Communication Theory of Secrecy Systems Shortly thereafter he and Warren Weaver published a book entitled Mathematical Theory of Communication - Answer Claude Shannon Changes to one character in the plain text affect multiple characters in the ciphertext, unlike in historical algorithms (Caesar cipher, ATBASH, Vigenère) where each plain text character only affects one ciphertext character. - Answer Diffusion Attempts to make the relationship between the statistical frequencies of the ciphertext and the actual key as complex as possible by using a complex substitution algorithm. - Answer Confusion This term means that a small change yields large effects in the output, like an avalanche. This is Fiestel's variation on Claude Shannon's concept of diffusion. We will see Fiestel's ideas used in many of the block ciphers we explore in this module. - Answer Avalanche Symmetric algorithm encryption - Answer C = E(k,p) Symmetric algorithm decryption - Answer P = D(k,c) To perform the binary _____ operation, you take two binary numbers and compare them one place at a time. If both numbers have a one in both places, then the resultant number is a one. If not, then the resultant number is a zero. - Answer AND The binary ______ operation checks to see whether there is a one in either or both numbers in a given place. If so, then the resultant number is one. If not, the resultant number is zero. - Answer OR The binary ______ operation impacts your study of encryption the most. It checks to see whether there is a one in a number in a given place, but not in both numbers at that place. If it is in one number but not the other, then the resultant number is one. If not, the resultant number is zero. It has a very interesting property in that it is reversible. - Answer XOR Most symmetric ciphers use_________ as part of their process - Answer XORing There are two types of symmetric algorithms. They are ______________ and ______________. A block cipher literally encrypts the data in blocks. 64-bit blocks are quite common, although some algorithms (like AES) use larger blocks. For example, AES uses a 128-bit block. Stream ciphers encrypt the data as a stream, one bit at a time. - Answer block ciphers; stream ciphers The algorithm(s) needed to encrypt and decrypt a message. - Answer Cipher The random bits used in encrypting a message. - Answer Key The mathematical process used to alter a message and read it unintelligible by any but the intended party. - Answer Algorithm The Feistel Network DES 3DES AES Blowfish Serpent Twofish Skipjack IDEA CAST TEA SHARK - Answer Symmetric Block Cipher Algorithms Refers to the generation of sub keys from a single key. - Answer Key schedule Larger block sizes increase security. Larger key sizes increase security. If the round function is secure, then more rounds increase security. A True B False - Answer A This function is named after its inventor, the German-born physicist and cryptographer Horst Feistel. At the heart of many block ciphers is a Feistel function. So this makes it a good place to start with study of symmetric algorithms. This function forms the basis for many, if not most, block ciphers. This function starts by splitting the block of plaintext data (often 64 bits) into two parts (traditionally termed L0 and R0). Usually, the split is equal, and both sides are the same size. - Answer The Feistel Function A variation of the Feistel network called an ______________ cipher. They use a modified structure where L0 and R0 are not of equal lengths. This means that L0 might be 32 bits and R0 could be 64 bits (making a 96-bit block of text). This variation is actually used in the Skipjack algorithm. - Answer Unbalanced Feistel One of the oldest of the modern symmetric ciphers is________. It was a block cipher developed by IBM in the early 1970s and used as a U.S. government standard until the 1990s. IBM had originally developed a cipher called Lucifer, which was designed by Horst Feistel. When the U.S. government began seeking a standardized encryption algorithm, IBM worked with the National Security Agency (NSA) to alter Lucifer to fit the government's needs, thus it was created. As you may guess, it is a Feistel cipher. - Answer DES This is a variation of DES that simply XORs another 64-bit key to the plaintext before applying the DES algorithm. - Answer DESx _________ is designated as FIPS 197 and can have three different key sizes. They are: 128, 192, or 256 bits. This algorithm was developed by two Belgian cryptographers, Joan Daemen and Vincent Rijmen. Unlike both DES and 3DES, it is not based on a Feistel network. This algorithm uses a substitution-permutation matrix rather than a Feistel network. It also operates on a four-by-four column-major order matrix of bytes, called the state. - Answer AES In the SubBytes step, each byte in the matrix is substituted for another byte using an 8-bit substitution box, called the _____________. - Answer Rijndael S-box __________ is a symmetric block cipher that was designed in 1993 by Bruce Schneier. This cryptography algorithm is intended as a replacement for DES. Like DES, it is a 16-round Feistel cipher working on 64-bit blocks. However, unlike DES, it can have varying key sizes ranging from 32 bits to 448 bits. There are really two parts to this algorithm. The first part handles the expansion of the key. The second part actually encrypts the data. The key expansion is handled in several steps. The first step is to break the original key into a set of subkeys. Specifically, a key of no more than 448 bits is separated into 4,168 bytes. There is a P-array and four 32-bit S-boxes. The P-array contains 18 32-bit subkeys, while each S-box contains 256 entries. - Answer Blowfish Like Blowfish, _________ is a symmetric key block cipher which was a finalist in the AES contest. This algorithm was designed by Ross Anderson, Eli Biham, and Lars Knudsen. It has a block size of 128 bits and can have a key size of 128, 192, or 256 bits, much like AES. The algorithm is also a substitution-permutation network like AES. It uses 32 rounds working with a block of four 32-bit words. Each round applies one of eight 4-bit to 4-bit S-boxes 32 times in parallel. It was designed so that all operations can be executed in parallel. - Answer Serpent _________ uses a block size of 128 bits and key sizes up to 256 bits. It is a Feistel cipher. It was designed by Bruce Schneier, John Kelsey, Doug Whiting, David Wagner, Chris Hall, and Niels Ferguson. - Answer Twofish Designed by NSA for the clipper chip, ___________ uses an 80-bit key to encrypt or decrypt 64-bit data blocks. It is an unbalanced Feistel network with 32 rounds. - Answer Skipjack The_________________ is a block cipher. The algorithm was published in 1991 and was designed by James Massey and Xuejia Lai. It operates on 64-bit blocks and has a 128-bit key. The algorithm consists of a series of eight identical transformations (each round) and an output transformation. It was designed as a replacement for DES. - Answer International Data Encryption Algorithm (IDEA) ________________ was created by David Wheeler and Roger Needham and first publicly presented in 1994. It is a simple algorithm, easy to implement in code. It is a Feistel cipher that uses 64 rounds (note this is a suggestion, it can be implemented with fewer or more rounds). The rounds should be even since they are implemented in pairs called, cycles. it uses a 128-bit key operating on a 64-bit block. It also uses a constant that is defined as 232/the golden ratio. - Answer TEA, or Tiny Encryption Algorithm ___________ was invented by a team of cryptographers including Vincent Rijmen, Joan Daemen, Bart Preneel, Antoon Bosselaers, and Erik De Win. It uses a 64-bit block with a 128-bit key and operates in six rounds. - Answer SHARK The most basic encryption mode is the _________________. The message is divided into blocks and each block is encrypted separately. - Answer electronic codebook (ECB) mode When using _____________ mode, each block of plaintext is XORed with the previous ciphertext block before being encrypted. This means there is significantly more randomness in the final ciphertext. This is much more secure than electronic codebook mode and is the most common mode. - Answer cipher-block chaining (CBC) In _____________, the previous ciphertext block is encrypted then the ciphertext produced is XORed back with the plaintext to produce the current ciphertext block. Essentially it loops back on itself, increasing the randomness of the resultant ciphertext. Allows encryption of partial blocks rather than requiring full blocks for encryption. This eliminates the need to pad a block like in CBC. - Answer cipher feedback mode (CFB) The _____________ mode turns a block cipher into a synchronous stream cipher. It generates keystream blocks, which are then XORed with the plaintext blocks to get the ciphertext. - Answer output feedback (OFB) __________________) is also used to turn a block cipher into a stream cipher. This is much like OFB mode. CTR generates the next keystream block by encrypting successive values of a "counter." The counter can be any simple function that produces a sequence that is guaranteed not to repeat for a long time. - Answer Counter mode (CTR An ______________ is a fixed-size input to a cryptographic primitive that is random or pseudo-random. It is added to a cryptographic algorithm and key in order to increase the randomness of the resultant cipher text. - Answer initialization vector (IV) Stream ciphers are also sometimes called ________ ciphers. - Answer state Ron Rivest created this algorithm in 1987 and it stands for Ron's Cipher. It is the most widely used software stream cipher. The algorithm is used identically for encryption and decryption as the data stream is simply XORed with the key. It uses a variable length key from 1 to 256 bytes. That key constitutes a state table that is used for subsequent generation of pseudo-random bytes and then to generate a pseudo-random stream which is XORed with the plaintext to produce the ciphertext. It generates a pseudo-random stream of bits. - Answer RC4 Published by the German engineering firm Seimans in 1993 The__________ (FIbonacci SHrinking) cipher is a software-based stream cipher using the Lagged Fibonacci generator along with a concept borrowed from the shrinking generator ciphers - Answer FISH This algorithm was published in a paper by Ross Anderson as an improvement on FISH. Anderson showed that Fish was vulnerable to known plaintext attacks. It is both faster and stronger than FISH. - Answer PIKE A _______ function H is a function that takes a variable-size input m and returns a fixed-size string. The value that is returned is called the hash value h or the digest. This can be expressed mathematically as h = H(m). An example of this is Windows will store that in the Security Accounts Manager (SAM) file in the Windows System directory. When you log on, Windows cannot "un-hash: your password (remember it is one way). So, what Windows does is take whatever password you type in, hash it, then compare the result with what is in the SAM file. If they match (exactly), then you can log in. - Answer hash In relationship to hashing, the term "________" refers to random bits that are used as one of the inputs to the hash. Furthermore, it complicates dictionary attacks that use pre-encryption of dictionary entries. It also is very effective against rainbow table attacks. - Answer salt This is a 160-bit hash function which resembles the earlier MD5 algorithm. This was designed by the NSA to be part of the digital signature algorithm. - Answer SHA-1 This is actually two similar hash functions, with different block sizes, known as SHA256 and SHA-512. They differ in the word size; SHA-256 uses 32-byte (256 bit) words where SHA-512 uses 64-byte (512 bit) words. There are also truncated versions of each standardized, known as SHA-224 and SHA-384. These were also designed by the NSA. - Answer SHA-2 This is a proposed hash function standard still in development. This is being chosen in a public review process from non-government designers. An ongoing NIST hash function competition is scheduled to end with the selection of a winning function, which will be given the name SHA-3 in 2012. - Answer SHA-3 This hash function uses 512-bit blocks and implements preset constants that change after each repetition. Each block is hashed into a 256-bit block through four branches that divides each 512 block into sixteen 32-bit words that are further encrypted and rearranged. Because the four branches are used in parallel, whereas SHA-256 uses four serial rounds, ____________ is hard to analyze. - Answer FORK-256 ____________________________ is a 160-bit hash algorithm developed by Hans Dobbertin, Antoon Bosselaers, and Bart Preneel. There exist 128-, 256-, and 320-bit versions of this algorithm, called RIPEMD-128, RIPEMD-256, and RIPEMD-320, respectively. These all replace the original RIPEMD which was found to have collision issues. The larger bit sizes make this far more secure that MD5 or RIPEMD. - Answer RACE Integrity Primitives Evaluation Message Digest (RIPEMD-160) The input message is broken into 512-byte chunks (16-32 bit integers). The message is padded with zeros if needed to reach 512-byte chunks. The length of the message (before padding) is then appended as the last 64 bits of the message. The algorithm operates on a 128-bit state, divided into four 32-bit words, denoted A, B, C, and D. They are initialized to an initial variable. The algorithm consists of four stages or rounds, each of which consists of 16 similar operations. Those operations are a non-linear function F, a modular operation, and a shift. - Answer The MD5 Algorithm This hash algorithm was initially defined in the Russian national standard and produces a fixed-length output of 256 bits. The input message is broken up into chunks of 256-bit blocks. If a block is less than 256 bits, then the message is padded by appending as many zeros to it as are required to bring the length of the message up to 256 bits. The remaining bits are filled up with a 256-bit integer arithmetic sum of all previously hashed blocks and then a 256-bit integer representing the length of the original message, in bits, is produced. - Answer GOST This hash function was designed by Ross Anderson and Eli Biham in 1995 and is 192 bits. It is designed using the Merkle-Damgård construction (sometimes call the Merkle-Damgård paradigm). This is a method to build collision-resistant cryptographic hash functions from collision-resistant one-way compression functions. The Merkle-Damgård construction was described in Ralph Merkle's Ph.D. dissertation in 1979. - Answer TIGER An ________________________ adds a key to a hash to improve integrity. - Answer HMAC or Hash Message Authentication Code A __________________, uses a block cipher in CBC mode to improve integrity. - Answer MAC or Message Authentication Code In PKI, Bob encrypts the message with Alice's _______________ and sends it. When Alice receives the message, they can decrypt it with her ________________. - Answer public key; private key In information theory,__________ is a measure of the uncertainty associated with a random variable. - Answer entropy Related to entropy, ________________ states: it is impossible to compress the data such that the code rate is less than the Shannon entropy of the source, without it being virtually certain that information will be lost. - Answer Shannon's source coding theorem Mn - 2^(n) -1 Where n is a prime number Works for n 2, 3, 5, 7 but fails on n = 11 and on many other n value - Answer Mersenne Primes Fn = 2^(2n) + 1 So, F1 = 221 + 1 or 5 However, F5 is not prime - Answer Fermat Numbers A _____________ is a number that has no factors in common with another number. - Answer co-prime The number of positive integers less than or equal to n that are co-prime to n is called the _____________ of n. So for the number 6, 4 and 5 are co-prime with 6. Therefore, ______________ = 2. - Answer Euler's totient With just 23 people in the room, you have a 50 percent chance that 2 will have the same birthday. - Answer Birthday Paradox The idea of the __________________ is to attempt to find a collision for a given hash. Now assume the hash is MD5, with a 128-bit output. You would have to try 2^128 possible hashes to guarantee a collision. That is a very large number. In decimal notation that is 3.e+38 Now from the birthday paradox we know that we actually need about 1.174√2^128 or .184. - Answer Birthday Attack Developed and published by Whitfield Diffieand Martin Hellman in 1976, ______________ is a cryptographic protocol that allows two parties to establish a shared key over an insecure channel. It was the first publically described asymmetric algorithm and is often used for the key exchange of symmetric keys. - Answer DiffieHellman This algorithm was first described in 1985 by Victor Miller (IBM) and Neil Koblitz (University of Washington). It is based on equations of the form: y2 = x3 + Ax + B - Answer Elliptic Curve Cryptography This algorithm is based on Diffie-Hellman and was invented in 1984 by Taher Elgamal. It is used in some PGP implementations as well as GNU Privacy Guard software. The algorithm consists of three parts: the key generator, the encryption algorithm, and the decryption algorithm. - Answer Elgamal FIPS 140 covers what? - Answer Cryptographic Modules FIPS 186 covers what? - Answer Digital Signatures FIPS 197 covers what? - Answer AES Table look-up Hardware Algorithmic (software) - Answer The 3 Types of Generators FIPS 201 covers what? - Answer Identity Verification What provides all 3 of the following? -Authentication -Integrity -Non-repudiatio - Answer Good digital signature schemes A ___________________ is an entity trusted by one or more users to manage certificates - Answer CA (Certification Authority) A ___________________ is used to take the burden off of a CA by handling verification prior to certificates being issued. It acts as a proxy between a user and CA and it receives a request, authenticates it and forwards it to the CA. - Answer RA (Registration Authority) A _________________ is a set of rules that defines how a certificate may be used. - Answer CP (Certificate Policy) __________ is an international standard for the format and information contained in a digital certificate and is the most common type of digital certificate in the world. It was first issued on July 3, 1988. It is a digital document that contains a public key signed by the trusted third party, which is known as a Certificate Authority, or CA. Relied on by S/MIME, it contains your name, info about you, and signature of the person who issued the certificate. - Answer X.509 HTTPS means _________________ with either SSL (older) or TLS (newer). The certificate must be installed on the web server for the website to use it. - Answer HTTP secured _______________ is the simplest form of authentication where the user's name and password are transmitted over a network and compared to a table of namepassword pairs. Typically, the passwords stored in the table are encrypted; however, the transmissions of the passwords are in cleartext, unencrypted. This is it's main weakness. The Basic Authentication feature built into HTTP uses this form of authentication. - Answer Password Authentication Protocol (PAP) ____________________________ calculates a hash after the user has logged in, then it shares that hash with the client system. Periodically, the server will ask the client to provide that hash (this is the challenge part). If the client cannot, then it is clear that the communications have been compromised. - Answer Challenge HandShake Authentication Protocol (CHAP) ____________is used widely, particularly with Microsoft operating systems. It was invented at MIT and derives its name from the mythical three-headed dog that was reputed to guard the gates of Hades. The client authenticates to the authentication server once using a long-term shared secret (e.g. a password) and receives a ticketgranting server from the authentication server. The tickets are time-stamped. This allows you to make additional requests using the same ticket within a certain time period (typically, eight hours). Uses symmetric cryptography Authentication is UDP port 88 - Answer Kerberos A server or client that Kerberos can assign tickets to. Basically, any machine that can be assigned tickets is known as a _____________________. - Answer Principal A server that authorizes the principal and connects them to the ticket granting server. - Answer Authentication Server (AS) Provides tickets - Answer Ticket Granting Server (TGS) The ticket that is granted during the authentication process. - Answer Ticket Granting Ticket (TGT) Used to authenticate to the server. Contains the identity of the client, the session key, the timestamp, and the checksum. It is encrypted with the server's key. - Answer Ticket ____________ uses the stream cipher RC4 (128 bit or 256 bit). For a 24-bit IV, there is a 50% probability the same IV will repeat after 5000 packets - Answer WEP (Wired Equivalent Privacy) _____ was developed by Netscape and has since been supplanted by TLS. It was the preferred method used with secure websites (i.e. https). - Answer SSL _________________ is a protocol for encrypting transmissions. A client and server negotiate a connection by using a handshaking procedure, in which the client and server agree on various parameters used to establish the connection's security. - Answer Transport Layer Security (TLS) Microsoft provides a system for encrypting partitions or entire hard drives using a Trusted Platform Module (TPM). By default, it uses the AES encryption algorithm with a 128-bit key. - Answer Bitlocker _________________ is the art and science of writing hidden messages in such a way that no one, apart from the sender and intended recipient, suspects the existence of the message. It is a form of security through obscurity. By altering the least significant bit, one can hide additional data without altering the original file in any noticeable way. - Answer Steganography Payload - The data to be covertly communicated, the message you wish to hide Carrier - The signal, stream, or data file into which the payload is hidden Channel - The type of medium used. This may be still photos, video, or sound files - Answer Steganography Terms The most common steganography method is _____________________. - Answer Least Significant Bits (LSB) This method of Audio Steganography (Steganophony) adds an extra sound to an echo inside an audio file, that extra sound conceals information. - Answer Echo hiding The NSA classifies Suite A cryptographies as published, while Suite B as not published. NSA Suite A cryptography contains classified algorithms that will not be released. These algorithms are used to encrypt especially sensitive information. Suite B are publically described algorithms. A True B False - Answer A This is the most basic tool for breaking most classical ciphers. In natural languages, certain letters of the alphabet appear more frequently than others. By examining those frequencies, you can derive some information about the key that was used. This method is very effective against classic ciphers like Caesar, Vigenère, etc. It is far less effective against modern methods. - Answer Frequency Analysis In a ____________________, the attacker obtains the ciphertexts corresponding to a set of plaintexts. This can allow the attacker to attempt to derive the key used and thus decrypt other messages encrypted with that key. - Answer Chosen plaintext attack A ____________________ is less effective, but much more likely for the attacker since the attacker only has access to a collection of ciphertexts. NOTE: The attacker ONLY has access to the ciphertext of messages. - Answer Ciphertext-only attack The __________________ is similar to the chosen-plaintext attack, except the attacker can obtain ciphertexts encrypted under two different keys. (the keys need to be related, meaning that one was derived from the other as is the case in wireless systems) - Answer Related-key attack A known-plaintext attack and uses a linear approximation to describe the behavior of the block cipher. Given sufficient pairs of plaintext and corresponding ciphertext, bits of information about the key can be obtained and increased amounts of data will usually give a higher probability of success. Invented by Mitsarue Matsui. - Answer Linear Cryptanalysis __________________ is a form of cryptanalysis applicable to symmetric key algorithms and was invented by Eli Biham and Adi Shamir. Essentially, it is the examination of differences in an input and how that affects the resultant difference in the output. It originally worked only with chosen plaintext. It could also work with known plaintext and ciphertext. - Answer Differential cryptanalysis Similar to Differential Cryptanalysis, but uses a different technique. Uses sets or even multisets of chosen plaintexts of which part is held constant and another part varies through all possibilities. - Answer Integral cryptanalysis The attacker deduces the secret key. - Answer Total break The attacker discovers a functionally equivalent algorithm for encryption and decryption, but without learning the key. - Answer Global deduction The attacker discovers additional plaintexts (or ciphertexts) not previously known. - Answer Instance (local) deduction The attacker gains some Shannon information about plaintexts (or ciphertexts) not previously known. - Answer Information deduction The attacker can distinguish the cipher from a random permutation. - Answer Distinguishing algorithm In 1980, Martin Hellman described a cryptanalytic time-memory trade-off which reduces the time of cryptanalysis by using pre-calculated data stored in memory. Essentially, these types of password crackers are working with pre-calculated hashes of all passwords available within a certain character space, be that a-z, or azA-z, or a-zA-Z0-9, etc. These files are called ___________________. They are particularly useful when trying to crack hashes. Since a hash is a one-way function, the way to break it is to attempt to find a match. The attacker takes the hashed value and searches the rainbow tables seeking a match to the hash. If one is found, then the original text for the hash is found. A popular hacking tool is Ophcrack. - Answer Rainbow Tables Windows stores passwords as a hash in a file called a _____ file. As you should know by now, a hash cannot be un-hashed. However, as you have seen, Rainbow Tables can be used to look up the matching password. - Answer SAM Time - The number of "primitive operations" which must be performed. This is quite loose; primitive operations could be basic computer instructions, such as addition, XOR, shift, and so forth, or entire encryption methods. Memory - The amount of storage required to perform the attack. Data - The quantity of plaintexts and ciphertexts required. - Answer The 3 resources for cryptanalysis A one-way mathematical operation that reduces a message or data file into a smaller fixed length output, or hash value. Variable data input (of any size) + hashing algorithm = fixed bit stream output (hash value) MD5 = 128 bits SHA1 = 160 bits - Answer Hash Function Different encryption keys generate the same ciphertext from the same plaintext message. - Answer Key clustering The time and effort required to break a protective measure. - Answer Work factor Each block of plaintext is XORed with the XOR of the previous plaintext block and the previous ciphertext block before being encrypted. As with CBC mode, an initialization vector is used in the first block. - Answer Propagating Cipher Block Chaining (PCBC) A number that has no factors in common with another number (3 & 7) - Answer Coprime numbers Developed in 1977 by three mathematicians, Ron Rivest, Adi Shamir, and Len Adleman. Based on the practical difficulty of factoring the product of two large prime numbers. Key sizes are typically from 1,024 - 4,096 bits. - Answer RSA Works at Layer 2 of the OSI model. Offers the ability to encrypt and authenticate. Uses EAP and/or CHAP to authenticate. Uses Microsoft Point to Point Encryption (MPPE) for encryption. (MPPE is a derived version of DES). ONLY works over standard IP Networks. - Answer Point to Point Tunneling Protocol (PPTP) Works at Layer 2 of the OSI model. Combination of PPTP and Cisco's Layer 2 Forwarding Protocol (L2F). Offers additional methods for authentication; PPTP offers two, whereas L2TP offers five. In addition to CHAP and EAP, L2TP offers PAP, SPAP, and MS-CHAP. L2TP works over standard IP networks, but also X.25 and ATM. - Answer Layer 2 Tunneling Protocol (L2TP) A variation on frequency analysis that is used to attack polyaplhabetic substitution ciphers. - Answer Kasiski test