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Fig; Encryption and Decryption 
E{P,K} 
D{C,K} 
Plain 
Cipher Text(C) 
Secret key(K) 
Secret 
Plain 
ISRJournals and Publications
Page 116

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International Journal of Advanced Research in
Computer Networking,Wireless and Mobile Communications
Volume: 2 Issue: 3 26-Jul-2014,ISSN_NO: 2320-7248
 
For encryption there are several secret key algorithms were implemented. In every 
algorithm there are two key techniques known as Substitution and permutation.
Substitution is the simple mapping of one value to another. Permutation is the process to re 
ordering the bit positions for each input. The techniques used in number iterations called 
rounds. The security of the data depends upon the rounds i..e, more increasing the number 
of rounds which may more secure the algorithm. To enhance the security they introduced 
non- linearity for encryption so as to difficult for decryption without the secret key. This is 
achieved with the s- boxes basically they are non- linear substitution tables. One of the 
major problems with this is the key distribution. The solution for this problem is available 
in public key cryptography. 
In most encryption schemes Data Encryption Standard expects two inputs one is plain text 
to be encrypted and secret key. The procedure is which the plaintext is accepted and the 
key arrangement for both encryption and decryption. Data encryption standard is a 
symmetric 64 bit block cipher as it uses same key for both encryption and decryption and 
operates only 64 bit block of data at a time. The key size is 56 bits however the actual 
input of the key is 64 bit only. All blocks are numbered from left to right which makes the 
eight bit of each byte the parity bit. 
Blowfish is a symmetric block cipher that can be effectively used for encryption and 
safeguarding of data. It takes a variable length key, from 32 bits to 448 bits. Blow fish 
was designed in 1993 by Bruce schneier as a fast, free alternate to the existing encryption 
algorithms. Blow fish is a fiestal network which contains 16 iterations. The block size is 
64 bits and the key length varies up to 448 bits. Blow fish is a variable – length key block 
cipher and suitable for non change key situations.