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BLOCK CIPHER SYSTEMS OPERATION MODES OF DATA ENCRYPTION STANDARD (DES)

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Presentation on theme: "BLOCK CIPHER SYSTEMS OPERATION MODES OF DATA ENCRYPTION STANDARD (DES)"— Presentation transcript:

1 BLOCK CIPHER SYSTEMS OPERATION MODES OF DATA ENCRYPTION STANDARD (DES)

2 DES Decryption (DES -1 ) : The same function used for encryption and decryption except if encryption keys are (K1, K2, …, K16) then the decryption keys are (K16, K15, …, K1) and in spite of cyclic shift left used in encryption the cyclic right shift is used in decryption. cyclic right shiftCyclic left shift decryption encryption

3 OPERATION MODES OF DES : 1- Electronic Code Book (ECB). 2- Cipher Block Chaining ( CBC). 3- Cipher Feed Back (CFB). 4- Output Feed Back (OFB).

4 56 bit key + 8 parity bit DES block encryption DES block decryption Data Storage Device 64 bit block of ciphertext in stage medium 64 bit block of plaintext 1- Electronic Code Book (ECB).

5 2- Cipher Block Chaining ( CBC).

6 3- Cipher Feed Back (CFB).

7 4- Output Feed Back (OFB).

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