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| encryption scheme where words and phrases in the P.T. message are replaced with words, numbers, or symbols, to create the C.T. message |
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| A method of replacing symbols in a language or message for the purpose of transmitting or storing the message using a particular method; generally, widely published and is not intended to secure information |
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| encrypted form of the plain text message |
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| Uses the same key for encryption and decryption. The key must be shared between the communicator prior to sending enciphered messages |
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| uses different keys for encryption and decryption. These keys often take the form of key pairs where one key is published and the other key is private. |
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| any organization established, usually by a government, for the purpose of performing cryptanalysis on foreign communications of interest. |
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| a field cipher used by the Germans during World War II. The Enigma is one of the better known historical encryption machines, and it actually refers to a range of similar cipher machines |
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| German rotor stream cipher machines used by the German Army during World War II |
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| is an electro-mechanical stream cipher device used for encrypting and decrypting secret messages |
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| device or object needed to encrypt the message, example scytale |
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| manual polyalphabetic substitution cipher system, invented in 1795 by Thomas Jefferson |
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| Cylindrical device employing a tape to scramble the letters in a message |
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| a symmetric-key block cipher algorithm and U.S. government standard for secure and classified data encryption and decryption. |
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| a symmetric-key algorithm for the encryption of electronic data, a block cipher, meaning a cryptographic key and algorithm are applied to a block of data simultaneously rather than one bit at a time |
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| a cryptosystem for public-key encryption, and is widely used for securing sensitive data, particularly when being sent over an insecure network such as the Internet. First described in 1977 by Ron Rivest, Adi Shamir and Leonard Adleman of the Massachusetts Institute of Technology. |
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| substitution in cryptography that uses a single substitution alphabet so that each plaintext letter always has the same cipher equivalent |
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| a system of substitution that mixes together a number of cipher alphabets in a cryptogram so that each plaintext letter is represented by a cipher that repeatedly changes |
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| a polyalphabetic cipher because it uses two or more cipher alphabets to encrypt the data. |
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| a pair of consecutive written units such as letters, syllables, or words |
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| a group of three consecutive written units such as letters, syllables, or words |
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| some piece of information employed by a cipher to guide the conversion of the P.T. to C.T. and vice versa |
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| the set of all possible keys that can be used to initialize it |
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| science of building new cryptosystems |
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| science of discovering weaknesses in existing cryptosystems in order to retrieve the plaintext of a message without knowing the key |
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| an encryption technique that cannot be cracked, but requires the use of a one-time pre-shared key the same size as, or longer than, the message being sent. |
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| means the cipher should hide all the local patterns or characteristics of the plaintext language |
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| means that the cipher should mix up segments of the message so that no character remains in its original position |
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| was an electro-mechanical device used by British cryptologists to help decipher German Enigma-machine-encrypted secret messages during World War II |
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| Machine used to decipher the Lorenz |
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| a word, phrase, or sentence formed from another by rearranging its letters |
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| a cipher which incorporates the message (the plaintext) into the key. The key is generated from the message in some automated fashion, sometimes by selecting certain letters from the text, or more commonly, by adding a short primer key to the front of the message. |
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| A unit of information, one hundredth of a ban |
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| a mode of operation for a block cipher, with the characteristic that each possible block of plaintext has a defined corresponding ciphertext value and vice versa. In other words, the same plaintext value will always result in the same ciphertext value. |
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| an error-detecting code commonly used in digital networks and storage devices to detect accidental changes to raw data. Blocks of data entering these systems get a short check value attached, based on the remainder of a polynomial division of their contents. |
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| a type of electronic signature that encrypts documents with digital codes that are particularly difficult to duplicate. |
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| the number of positive integers that are relatively prime to (i.e., do not contain any factor in common with) where 1 is counted as being relatively prime to all numbers. |
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| a measure of how similar a frequency distribution is to the uniform distribution. |
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| Linear Feedback Shift Register |
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| shift register whose input bit is a linear function of its previous state. The most commonly used linear function of single bits is exclusive-or (XOR) |
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| is a method of attacking polyalphabetic substitution ciphers, such as the Vigenère cipher. Relies on the occasional coincidental alignment of letter groups in plaintext with the keyword, find groups of same letters of 3 or more and calculate the distance between those groups. |
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| a cryptographic hash function containing a string of digits created by a one-way hashing formula that takes an input of arbitrary length and produces a message digest that is 128 bits long. |
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| a mode of operation for a block cipher. It has some similarities to the ciphertext feedback mode in that it permits encryption of differing block sizes, but has the key difference that the output of the encryption block function is the feedback (instead of the ciphertext). |
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| a way to take data that may or may not be a multiple of the block size for a cipher and extend it out so that it is. |
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| states that if n items are put into m containers, with n > m, then at least one container must contain more than one item. |
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| Pretty Good Privacy (PGP) |
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| an encryption program that provides cryptographic privacy and authentication for data communication. |
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| combines two or more ciphers processes with the intent that the resulting cipher is more secure than the individual ciphers alone |
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| an encryption technique that uses a paired public and private key (or asymmetric key) algorithm for secure data communication. |
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| gathering information through observations of operations of the underlying cipher that can leak performance characteristics |
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| A function that is easy to compute in one direction but difficult to compute in the opposite direction (finding its inverse) without special information. |
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| a symmetric key cipher operating on fixed-length groups of bits called blocks |
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| An analysis of the frequency that letters occur in a message and a simple but powerful cryptanalysis tool |
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| The largest divisible factor of two numbers |
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| An encryption method where the mapping of the permutation to the natural ordering of the alphabet denotes the key. |
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