SECURING FIBRE CHANNEL FABRICS - Brocade

Cryptographic Algorithms• Range of applications. Ability to implement in a wide range ofdevices, from supercomputers and disk arrays to Smart Cards andradio-frequency identification (RFID) devices, can determine thevalue of an algorithm.• Cost. If the cost to implement the cryptosystem is too high, it maynot find commercial relevance. Military and intelligence applicationssometimes warrant the high cost in exchange for strongercryptographic capabilities.• Openness. In support of Kerckhoffs' principle stated by AugusteKerckhoffs in the 19th century: a cryptosystem should be secureeven if everything about the system, except the key, is publicknowledge.There are three basic categories of ciphers: block ciphers, streamciphers, and hashing algorithms.Block CiphersBlock ciphers are used to encrypt data as an entire block as opposedto one bit at a time. An entire block of data is processed at the sametime by the block cipher. A plaintext message is broken down intofixed-length blocks and passed to the block cipher as plaintext. Eachplaintext block is encrypted with they key to create a ciphertext blockthat is the same size as the input plaintext block. The decryption processtakes the ciphertext message and breaks it down into fixed-sizeblocks. Each ciphertext block is decrypted using the key to produce aplaintext block the same size as the input ciphertext block, as shownin Figure 28.Figure 2. Block cipher encryption/decryptionSecuring Fibre Channel Fabrics 79