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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 


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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. 


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Process of validating the identity of the user or program that is requesting access to a computing resource 


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Secret key ciphers are often classified as block or stream ciphers. Whereas a block cipher operates on a fixedlength 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. 


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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. 


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Its origin in the Arabic word sifr, suggesting the concealment of clear meaning 


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A text that is "garbled" and therefore needs to be decoded into original (plaintext) from before use 


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Cryptographic techniques allow you to hide your secrets, preserving confidentiality. 


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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. 


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A person who tries to break the code without having access to the key. Often refers to hackers or ethical hackers. 


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An expert in the field of design and use of cryptographic techniques 


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The field that offers techniques and methods of managing secrets 


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A person who is either a cryptographer or cryptanalyst 


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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 


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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. 


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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. 


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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 


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Either one condition or the other is true, but not both conditions 


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The value of a variable that drives encryption or decryption 


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Key distribution center (KDC) 

Definition
A trusted third party that functions as a custodian of secret keys 


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A fixedlength output created from a message of any length 


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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. 


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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. 


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A fourth purpose of cryptography is nonrepudiation, the assurance that the sender will not be able to deny transfer of the message. 


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Definition
The cryptographic method of onetime pads uses the Vigenere Tableau discussed earlier. THe only difference is that instead of fixedlength key, the key used is a long as teh message itself. It is unlikely to repeat any patters, unlike a fixedlength 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. 


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Definition
A text is humanly readable form. Refers to the original message that is enrypted for secrure transmission or storage. Also called cleartext. 


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Public key cryptography (PKC) 

Definition
An approach to cryptography that uses a pair of related keys, a public and a private key. 


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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. 


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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. 


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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 


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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. 


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Definition


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A transposition requires moving plaintext (or ciphertext) characters backward and forward ina predetermined order. 


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A cipher created by changing the order of the plaintext characters in the ciphertext 


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An example of a polyalphabetic substitutin cipher 

