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This lab had been covered with this topic :
• Explain What is Symmetric and Asymmetric Cryptography
• Implementing Caesar Cipher for Symmetric Cryptography.
• Implementing Vigeneré Cipher for Symmetric Cryptography.
• Implementing RSA algorithm for Asymmetric Cryptography



For me, Symmetric crptography is the both paties involved in the communication use same key but secretly between them. That why we can called is as shared secret system or private key systems. The operation of this symmetric separated into strem ciphers and block ciphers. But the huge problem of this cyptography is key exchange. Different to assymmetric, means public key cyprography. This asymmetric works when people that has private key will keep it secretly then anyone is told the public key will enable them to unlock the private key and read the data that had been sent.



The comparison between symmetric and assymetric is symmetric key usually faster to use in electronically than asymmetric. But assymetric usually more computationally. Both of this key is related to each other and especially in mathematically related.There are a few example of symmetric ciphers such as Data Encyption Standard (DES), RSA and AES. While the popular example of assymetric is PGP(Pretty Good Privacy).



Caesar ciphers is the action of replace each plaintext letter with one a fixed number of places down the alphabet.






(Source from: http://www.wikipedia.com/)

Example of SHIFT 3 in Caesar Cipher :
Plain: ABCDEFGHIJKLMNOPQRSTUVWXYZ
Cipher: DEFGHIJKLMNOPQRSTUVWXYZABC

Example how to solve the problem :
Plaintext: the quick brown fox jumps over the lazy dog
Ciphertext: WKH TXLFN EURZQ IRA MXPSV RYHU WKH ODCB GRJ

Vigenere ciphers is polyalphabetic cipher based on using successively shifted aphabets, means a different shifted alphabetic and the step is based on the tableau and use the keyword. It use a series of different caesar cipher. This cipher is well known because we easy to understand and use it.

Here is the simple step of implementing RSA algorithm for Asymmetric Cryptography :

1. value for p, q had been given
2. n = p x q
3.φ(n) = (p – 1) (q – 1).
4.d= e -1 mod φ(n)