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### 50 Cards in this Set

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 Cryptanalysis Breaking or cracking the code and deciphering the data without authorization Cryptosystem A system for encoding and deciphering data. Decipher To decode the data Encipher To code the data Keyspace The group of numbers used to create a key. Non-repudiation Ensuring that the message sender is tracked and stored as having sent the message. Work Factor Estimated amount of work it would take to break the code. What are the 4 primary goals of cryptography? Confidentiality, Integrity, Authentication, and non-repudiation. Differential Cryptanalysis Compares two plain text data sets suring encryption to determine probably keys. Often used against block ciphers. Factoring Attempting to determine the prime factors of the keys. Linear Cryptanalysis Compares known plain text and ciphertext to determine probably keys Man-in-the-middle Intercepting messages between the sender and receiver Meet-in-the-middle Compares known plaintext and keys to intercepted encrypted text. Substitution A method of encoding data that uses the alphabet and each letter's associated numbers. Predetermined pattern. Ceaser Cipher Common form of substitution. Moves each letter 3 places forward in relation to its number. Polyalphabetic Cipher Uses multiple alphabets to encode data. (i.e. vigenere cipher) Transposition A method of encoding data that scrambles the letters of the message. a/k/a - Permutation Concealment Cipher A predetermined key or groups of words used to decode a message, such as reading only every fourth word. Running Key Cipher Using some predetermined set of actions taken to decode a message. Steganography Photographs or other digitial media used to hide messages. Symmetric Key Cryptography A method of encoding data that uses a single key. Used by both sender and receiver. Good to use with large amounts of data and is faster than Asymmetric Key Escrow Form of symmetric key cryptography used by law enforcement. Third party agency maintains the key. Clipper Chip An encryption chip for digital voice communications that automatically encrypts and decrpyts. Block Cipher An encryption method that breaks the message into blocks of data bits. Each block is encoded. Stream Cipher An ecryption method that breaks the message into a stream of single bits. Each bit is encoded. Slow method Data Encryption Standard (DES) 56 bit cipher key for symmetric key encryption. Remaining 8 bits are used for parity, performed through 16 rounds. Susceptible to brute force attacks Triple DES (3DES) Uses 112 bit cipher key for symmetric key encryption. Encrypts message 3 times. Advanced Encrption Standard (AES) Uses Rijndael Block Cipher. Incorporates variable block cipher and key lengths. Uses a key size of 128.192, or 256. Approved by government Name the 4 modes of DES 1. Cipher Block Chaining(CBC) - Most common. XORs an initialization block. 2. Cipher feedback(CF) - uses stream cipher 3. Electronic Code Book(ECB) - Uses Block ciphering 4. Output Feedback(OF) - Easy to break, XORs plain text Name the 3 modes of 3DES 1. DES-EDE2 - Encrypt with one key, decrypts with another, encrypts with the first key again. 2. DES-EEE2 - Encrypts with one key, encrypts with a 2nd key, encrypts with the first key 3. DES-EEE3 - Encrypts with one key, encrypts with a 2nd key, encrypts with a 3rd key. Rijndael Block Ciper Uses both variable block and key lengths determined by the implementation. The lengths can be either 128,192, or 256. Blowfish Block cipher with block lengths, encrypted thru 16 X of 64 bits and key lengths up to 448 bits. International Data Encryption Algorithm (IDEA) Block cipher with block lengths of 64 bits divided into 16 bit units and encrypted 8 X. key lengths of 128 bits RC5 Block cipher with variable block and key lengths and as well as encryption iterations RC6 Block cipher based on RC5. Uses a min. 128 block size and 2 working registers to comply with AES Twofish Block cipher with 128 bit block lengths, encrypted 16 X and key lengths up to 256 bits. Asymmetric Key Cryptography A method of encoding information that uses 2 keys and a one-way function. Public key encrypts, private key decrypts. can perform authenticatoin and non-repudiation. a/k/a public key cryptography Open Message Encrypts message with private key, provides authentication only. Secure Message Encrypts the message with public key, provides confidentiality only. Signed and Secure Message Encrypts the message with private key and then with public key, provides authentication and confidentiality Message Digest(Message Hash) Cryptographic data that verifies the contents of a message that has not been altered. What is the difference between keyed and non-keyed message digests? Keyed - original message combined with a secret key. (MACs) Non-Keyed - original message hashed without any other mechanisms(MICs and MDCs) Name some Message Digest Formats Message Digest 5 (MD5) Secure Hash Algorithm(SHA) Hashed Message Authentication Code (HMAC) Characteristics of a message hash 1. Set length signature is created from variable length input. 2. Slight change in orginal creates great difference in result signatures. 3. Chances of 2 differing input values produce the same output signatures are low. Asymmetric key algorithms 1. Diffie-Helman - requires key agreement 2. El Gamal - Functions on the encryption and digital signature. Often operates slowly. 3. Elliptic Curve Cryptosystem(ECC) - Often difficult to implement but capable to functioning with limited resources such as power and bandwidth. 4. Merkle-Hellman Knapsack - Applying weights to each set of items where the total defines the items in the knapsack. Used w/ trapdoors to one-way functions. 5. RSA - Functions on the encryption, digital signature, and key exchange. Public Key Infrastructure(PKI) Keys are created on the PC. Designed to address remote users and their data transmissions. common for e-commerce. Digital Signature Validates identity of sender. approved by NIST via SHS Name 4 Email Security Methods 1. Pretty Good Privacy(PGP) - uses PGP keys only 2. Privacy Enhanced Mail(PEM) - can use various keys 3. Multipurpose Internet Mail Extension(MIME) - good choice for internal and standalone. No inherent security measures 4. Secure/MIME(SMIME) Name 5 Internet Security Methods 1. Internet Security Protocol(IPSec) - server to server, remote access, network protection. 2. Secure Electronic Transaction(SET) - transmitting credit card data 3. Secure Hypertext Transport Protocol(SHTTP) - Protects single pages 4. Secure Shell(SSH-2) - remote access over the network. 5. Secure Socket Layer(SSL) - client to server authentication (HTTPS) 2 Different protocols for IPSec 1. Authentication Header(AH) - provides authentication 2. Encapsulating Security Payload(ESP) - whole suite of security