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14 Cards in this Set
- Front
- Back
- 3rd side (hint)
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Symmetric Algorithm |
Des, 3Des, AES, RC-4, RC-5, 2fish, blow fish, IDEA, CAST, MARS |
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DES( Data encryption standard). It has five modes |
Block size : 64 bits Key size: 56 bits Rounds: 16 a. Electronic Code Book (ECB): least secure as it uses Secret key (Static) used for shortest transmission ( data units are encrypted) b. Cipher Block Chaining ( CBC): it uses block cipher. Uses IV and it has Chaining. Errors propogate. C. Cipher Feedback mode(CFB): it is stream cipher, uses IV , propogates error. D. Output feedback (OFB) : stream cipher, no chaining hencevit does not propogates errors. E. Counter mode(CtR): it is a stream cipher and helps in parallel computing . No chaining |
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Exam tip |
Output feedback mode OFB, and counter mode CTR, has no chaining hence it doesn't propogate errors. |
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2. Triple DES |
Key length : 3 * 56 = 168 bits A. DEs- EEE3{E= Encryption; 3 = Number of keys used} B. DEs- EDE3{ E= Encryption; D= Decryption ; 3 = Number of keys used} C. DES-EEE2{ E= Encryption; 2= Nber of keys used( Key length: 2*56=112 bits)} D. DES- EDE2{ E= Encryption ; D= Decryption; 2= Nber of keys used( Key length: 2*56= 112 bits} |
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IDEA( International data Encryption Algorithm ) PGP: pretty good privacy = is a good IDEA |
Bit block : 64 bits Key length: 128 bit ( works on Des principle) |
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4. Blowfish |
Bit block -64 bits, key length: 32-448 bits. Much faster than IDEA and DES |
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Skipjack |
Bit block : 64 bits, key= 80 bits. Support key escrow . Retained by NIST and dept. Of Treasury. |
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RC5 |
Rivest Cipher 5 , patented by Rivest, Shamir, adleman Block =( 32, 64, or 128), key length = 0-2040 bits |
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Advanced Encryption Standard (AES)/ Rijndel |
Replacement for DES. Allows block size equal to the key lenght Bit Block= 128 bits Key: 128 bits - 10 rounds Key : 192 bits -12 rounds Key: 256 bits -14 rounds |
Exam tip : best encryption for data at rest AES 256 |
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Two fish |
Bit block = 128 bits; key = 256 bits Uses two techniques Prewhitening Postwhitening |
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Creation and Distribution of keys |
-Offline - out of band -Public key encryption - uses public key to establish communication link -Diffie Hellman - Key exchange |
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Storage and Destruction of Keys |
Keys and encrypted data should be stored in different system For sensitive keys: use split knowledge, means two different individuals with half of the key. |
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Key escrow and recovery |
Secret key is divided into 2 halves and given to 3rd party . When government obtain legal authority , can combine 2 keys to create secret key. ( Fair crypto system) . This standard is the basis behind the Skipjack algorithm |
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Cryptographic Life cycle |
All cryptographic system has a life span ( except one time pad) |
Exam tip: each key should be changed periodicaly |
