Block Cyphers & Stream Cyphers

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Block Cyphers & Stream Cyphers Now that we’ve explained and demonstrated the basics of cryptography, let’s talk about cyphers.  This lesson discusses two types of cyphers, Block Cyphers and Stream Cyphers and then nicely demonstrates the differences in how they work. You’ll observe through a very detailed demonstration how a block cypher process works using a basic sentence.  Using the same sentence, you’ll learn how a stream cypher process works and you’ll learn an example of a Stream Cypher which you must know for the Security+ exam.  Good Stuff, don’t miss it. [toggle_content title="Transcript"] Next we look at the fundamental differences and encryption methods, we look at block Cypher compare them to stream Cypher. A block Cypher will take information to be processed and process it in block sizes, specific block sizes. You would be told that the block Cypher in either 56 bit blocks or 128 bit blocks. Whatever the block size is the block Cypher will proceed in this fashion. Let's assume we are using a block size of 4. It would take 4 characters at a time. So we take 1, 2 , 3, 4. That is one block. Encrypt that, it would then take the next block, another 4 characters: 1,2,3,4 and it does that. 3 And it does this until everything is exhausted in the message. This is how blocks cyphers will work. Stream cyphers on the other hand will take information to be encrypted individually or in bits. So a stream cypher will work in this fashion. Take that, encrypt it one at a time, individually or in bits we say. So stream cyphers work this way, encrypting one character at a time until the entire message is encrypted. For this syllabus, the only stream cypher we have to discuss is RC4. This will be requested on the exam, give an example of a Stream cypher. The answer to that will be RC4. RC4 is the only stream cypher we have for the syllabus and block cyphers; they process information by encrypting them in specific block sizes. [/toggle_content]
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