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Showing posts with label Networking. Show all posts
Showing posts with label Networking. Show all posts
Wednesday, February 4, 2015
Comparison between Symmetric key and Asymmetric key Cryptography(Lecture No. 2 Cryptography)

Lecture No. 2
Comparison between Symmetric key and Asymmetric key Cryptography
Encryption can be considered as electronic locking while decryption can be thought as electronic unlocking. The sender pass the message in a box using a key and the receiver unlocks it with the key and takes out the message.
So in symmetric key cryptography same key is used for locking and unlocking while in asymmetric key cryptography two different keys are used one key for locking and another key for unlocking.
Symmetric key cryptography (in detail)
Symmetric key Cryptography started thousands of years ago when people needed to exchange secrets. We still mainly use this one in our network security.
Today’s ciphers are much more complex. First we will discuss about traditional ciphers or algorithems which are character oriented. After this we will discuss the modern ones which are bit oriented.

Traditional ciphers
These are character oriented although these are now absolute; the goal is how modern ciphers evolved from them. We can divide tradition symmetric key ciphers into two brand categories
Categories of Traditional ciphers
11.       Substitution ciphers which is further divided in Monoalphabatic and polyalphabetic substitution ciphers.
22.       Transposition ciphers
These are two main categories of traditional ciphers will be discussed in detail in next lecture.

Continued ……… 

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Sunday, February 1, 2015
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What is cryptography in Networking?
Cryptography is used for Security Purposes in Networking.
Definition: It is the way of transforming messages to make them secure against attacks. It is a Greek word which means “Secret writing”
Components of Cryptography
1.Plain Text: This is the original message that  is not transformed yet. For message transforming first we will have an encryption algorithem that transforms plaintext into cipher text.
2.Cipher Text: After the message transformed is known as cipher text. Again message is converted from cipher text to plain text through an algorithem known as decryption algorithem.
3.Cipher: We refer both encryption and Decryption algorithem as cipher.
4.Key: A key is a number that the cipher used and operates on. For encryption we use encryption algorithem, plain text and encryption key , these will create a cipher text. While for decryption we use Decryption Algorithem . Decryption key and Cipher text and this will result in Plain text.
5. Alice , Bob and Eve
Alice is the person who sends the secure data. Bob is the Person who is being received the data or message. While eve is the person who intercept the data or make any change in it.
Categories of Cryptograph
It has two categories
1.       Symmetric key Cryptography(Secret key cryptography)                 
2.       Asymmetric key cryptography ( Public key cryptography)   
1.       Symmetric key Cryptography
In this type of cryptography same key is used for both encryption and decryption. Sender uses this key and  an encryption algorithem to encrypt the data  and the receiver also uses the same key and a decryption algorithem to decrypt data.
Note: Encryption is that when plain text converted into cipher text while Decryption is that when  cipher text is converted back into plain text.
2.       Asymmetric key Cryptography
In this type of cryptography two different keys are used a private key and a public key. Private key is used for  decryption and is kept by the receiver. While public key is used for decryption and is kept by the public.  

Continued in next lecture………….
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