Tuesday, August 18, 2009
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)
Sunday, August 16, 2009
A few propose of this operating system security such as multiprogramming had been introduced for the protection need..Some of purpose is for memory protection, means that prevents from corrupting the memory of another process running on the same computer and same time but we must allert with the method protection of memory.
There are seven of method :
- Fence
- Relocation
- Paging
- Segmentation
- Base/bound register
- tagged architecture
- paging combined with segmentation
Besides that, we must protecting general object by using file protection, group protection, access control limitation,permission, authentication and so on. Below is general object protection :
- Memory
- File/Data set on an auxiliary storage device
- Program Executing in memory
- A directory file
- Hardware device
Monday, August 10, 2009
Security??Something that support our life and make our life easy to handle. So some organization provide program security for us because of attack such as brute force attack, replay attack, man in the midle attack and fault in cryptosystem. Program security is important part that teach us how the malicious proram will effect our computer and how to manage it.Malicious program is something that corrupt our computer from running as usually.
We can detect it is virus if we don't see raw data, it can do harm and can also be confidential. There are a few type of viruses such as parasitic virus, memory-resident virus, boot sector virus, stealth virus,macro virus, directory virus,false virus, FAT virus and polymorphic virus. Resident is new for me, it means type of virus that hides permanently in RAM memory and it can control and intercept all of the operations carried out by the system. It can corrupt our file and program we opened, closed, copied, renamed and so on. Virus phase can be divided into 4phase.1st, Dormant Phase.2nd,Propagation Phase.3rd, triggering phase and 4th is execution phase.There are a few type of malicious attack such as :
