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Audit 2 - Exam 2
Chapter 5
36
Accounting
Graduate
03/15/2009

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Term
Advanced encryption standand (AES)
Definition
New symmetric key encryption standard that is efficient in terms of processing pwoer and memory and than can use key lengths of 128, 192, or 256 bits
Term
Algorithm
Definition
Every cipher has two components a cryptograpic method - also called a algorithm - and a key. A method is the procedure used to encrypt (and decrypt) the message.
Term
Authentication
Definition
Process of validating the identity of the user or program that is requesting access to a computing resource
Term
Block cipher
Definition
Secret key ciphers are often classified as block or stream ciphers. Whereas a block cipher operates on a fixed-length block of contiguous characters at a time. In a block cipher, a predetermined block of contiguous data is treated (encrypted) at a time; each block is considered independent, requiring the use of the key repeatedly for each block of data.
Term
Brute-force attack
Definition
Technique of trying to guess a password by running through a list of all possibilities. The attack is often used after dictionary attack fails to guess passwords.
Term
Cipher
Definition
Its origin in the Arabic word sifr, suggesting the concealment of clear meaning
Term
Ciphertext
Definition
A text that is "garbled" and therefore needs to be decoded into original (plaintext) from before use
Term
Confidentiality
Definition
Cryptographic techniques allow you to hide your secrets, preserving confidentiality.
Term
Confusion
Definition
At its most basic level, there are two ways of scrambling content: diffusion and confusion. Confusion is even more complication and involves complex transpositions and substitutions, as we shall see in the case of data encryption standard.
Term
Cryptanalyst
Definition
A person who tries to break the code without having access to the key. Often refers to hackers or ethical hackers.
Term
Cryptographer
Definition
An expert in the field of design and use of cryptographic techniques
Term
Cryptography
Definition
The field that offers techniques and methods of managing secrets
Term
Cryptologist
Definition
A person who is either a cryptographer or cryptanalyst
Term
Data encryption standard (DES)
Definition
A cipher that encrypts a block of bits in the plaintext at a time, using several substitutions and permutations in multiple iterations
Term
Decryption
Definition
Decription or decipherment, is the step where the intended recipient converts the ciphertext into the plaintext. Again, this person uses the scrambled message received (ciphertext), the method, and the key.
Term
Diffusion
Definition
At its most basic level, there are two ways of scrambling content: diffusion and confusion. Diffusion involves changing the order of characters in the message (transposition) plus one other addition function. This may be substitution, which involves replacement of each character in the message with another designated character.
Term
Encryption
Definition
The cryptographic procedure used to convert the plaintext into ciphertext to prevent anyone except the owner(s) or intended recipient(s) from reading the data
Term
Exclusive or (XOR)
Definition
Either one condition or the other is true, but not both conditions
Term
Key
Definition
The value of a variable that drives encryption or decryption
Term
Key distribution center (KDC)
Definition
A trusted third party that functions as a custodian of secret keys
Term
Message digest
Definition
A fixed-length output created from a message of any length
Term
Message integrity
Definition
A third purpose of cryptography is called message integrity. This is an assurance that the message is not modified in transit, and if it is, that the modification can be detected.
Term
Method
Definition
Every cipher has two components, a cryptogrpahic method - also called algorith - and a key. A method is the procedure used to encrypt (and decrypt) the message.
Term
Nonrepudiation
Definition
A fourth purpose of cryptography is nonrepudiation, the assurance that the sender will not be able to deny transfer of the message.
Term
One-time pad
Definition
The cryptographic method of one-time pads uses the Vigenere Tableau discussed earlier. THe only difference is that instead of fixed-length key, the key used is a long as teh message itself. It is unlikely to repeat any patters, unlike a fixed-length key, because the pad (number of characters in the key value) is generated by a random number generator. Both the sender and the receiver of the message have the same copy of the pad.
Term
Plaintext
Definition
A text is humanly readable form. Refers to the original message that is enrypted for secrure transmission or storage. Also called clear-text.
Term
Public key cryptography (PKC)
Definition
An approach to cryptography that uses a pair of related keys, a public and a private key.
Term
Rijandael encryption algorithm
Definition
Rijandel encryption algorithm became the secret key standard in June 2002. Rijndale is a block cipher with variable block length and key length. Three possible key lengths (128, 192, and 256 bits) can be combined with three choices of block length (128, 192, and 256 bits) to alllow users to pick one of nine possible pairs of key length and block length. Both key size (length) and block size can be easily extended in increments of 32 bits.
Term
RSA algorithm
Definition
An encryption algorithm, created by Rivest, Shamir, and Adelman, that uses the public key cryptography
Term
Simple substitution cipher
Definition
In simple substitution ciphers, one character of the plaintext is replaced by a designated character in the ciphertext. The weakness of monoalphabetic substitution cipher arises from the fact that for every character in the plaintext, a designated character is substituted. If you determine a frequency distribution of characters in the ciphertext, it will resemble the frequency distribution of the plaintext with one exception: characters are different. To address this limitation, more than one set of alphabetic substitutions can be used. Because more than one set of alphabetic substitutions is used, this scheme is called a polyalphabetic substitution cipher. The result is that the frequency distribution of the ciphertext characters is "flatter" and more difficult to use in guessing the plaintext characters from the ciphertext characters' frequency.
Term
Stream cipher
Definition
Secret key ciphers are often classified as block or stream ciphers. A stream cipher treats the message to be encrypted as one continuous stream of characters. The resulting cipher is called a stream cipher
Term
Subsitution
Definition
A substitution technique requires the substitution of each character in the plaintext with another predetermined character from the alphabet in the ciphertext, as in Caesar's cipher.
Term
Text
Definition
Content or a message
Term
Transposition
Definition
A transposition requires moving plaintext (or ciphertext) characters backward and forward ina predetermined order.
Term
Transposition cipher
Definition
A cipher created by changing the order of the plaintext characters in the ciphertext
Term
Vigenere cryptosystem
Definition
An example of a polyalphabetic substitutin cipher
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