Flashcards

Encryption

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Flashcards do conjunto (23)

1Using Encryption is essentialDefinitions
* Cryptography
*Cryptanalysis
*Encryption
*Decryption
2Cryptography- Process of making & using codes to secure transmission of information. Cryptography comes from Greek word kryptos, meaning "Hidden" & graphien meaning "To write".Cryptanalysis- the process of obtaining the original message (called the plaintext) from an encrypted message (called the ciphertext) without keys to perform encryption process.
3*ENCRYPTION* Process of converting an original message into a form that is unreadable to unauthorized individuals.*DECRYPTION*
Process of converting the ciphertext message back into plaintext so the message can be readily understood.
4Algorithm: Programmatic steps used to convert an encrypted message into an encrypted sequence. Cipher or cryptosystem: Encryption method or process encompassing the algorithm, keys & procedures used to perform encryption & decryption.Ciphertext or cryptogram: Encoded message resulting from an encryption.
Code: Process of converting components of an unencrypted message into encrypted components.
Decipher: Decrypt, decode ciphertext into plaintext.
Encipher: Encrypt, encode plaintext into ciphertext.
5Key or cryptovariable: Information used in conjunction with an algorithm to create the ciphertext from the plaintext. Keyspace: Entire range of values used to construct an key. Link encryption: Series of encryptions & decryptions between systems passing on the encrypted message until reaches destination.Plaintext or cleartext: Original unencrypted message.
Steganography: Hiding of messages
Work factor: Amount of effort required to perform cryptanalysis to decode an encrypted message.
6*Cipher Methods* - Bit stream - Block cipherBit stream - Each plaintext bit is transformed into ciphertext bit one at a time
Block cipher - Message divided into blocks, each is transformed into encrypted block of cipher bits using a key
7*Substitution Ciphers* -Monoalphabetic -Polyalphabetic -VigenereSubstitution cipher- Substitute one value for another
Monoalphabetic- Simple enough, uses one alphabet
8Polyalphabetic- More advanced, uses two or more alphabets Vigenere-Advanced cipher type that uses simple polyalphabetic code
9*Transposition Cipher* -Easy to understand -If properly used, produces ciphertext that is difficult to decipher-Rearranges values within a block to create ciphertext
-Can be done at bit level or at (character) byte level
-To strengthen encryption, keys and blocks can be increased to a larger size
10*Vernam Cipher* -Developed at AT&T -Uses set of characters, once per encryption process -Performs different encryption operations*Values are added numeric values, plaintext needs to be encrypted
*Each character is turned into a number, value for position is added
*Resulting sum for characters converted back to ciphertext for letter transmission
*if sum of two values exceeds 26 then 26 deducted from total
11*Book or Running Key Cipher* -Uses text as key to encrypt message -Ciphertext contains codes, associated with page, lines and word numbersAlgorithm is the mechanical process of...
-Looking up references from ciphertext
-Converting each reference to a word, by using the ciphertext's value and the key
Typical sources are dictionaries
12*Cryptographic Algorithms* -Symmetric-Symmetric Encryption-
Algorithm that uses the same key for both encryption & decryption. Key must be kept secret, is shared by message sender & recipient.
13-Asymmetric-Asymmetric Encryption-
Where keys come in pairs. What one key encrypts the other can only decrypt.
14True or False Web browsers do not use built-in secure encryption features for e-commerce.FALSE
15Cryptography originates from Greek word Kryptos.TRUE
16The science of encryption is known as protection.FALSE
17Identify the following Acronyms MACMessage Authentication Code
-Key dependent, one-way hash function
-Used in password verification to confirm identity of users
18SHSSecure Hash Standard
-Is a standard issued
19NISTNational Institute of Standards & Technology
20What is the science of encryption known as?Cryptology
21What is a algorithm?Programmatic steps used to convert an unencrypted message into encrypted sequence.
22Whats another name for the Vernam cipher?One time Pad
23Whats another name for Asymmetric Encryption?Public Key Encryption