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DESIGN DECISIONS: 
A 64 bit block size yields 32 bit word size and maintain the block size compatibility 
with existing algorithm. Blowfish is easy to scale up to 128 bits and down to smaller 
block sizes. 
The fiestal network that makes up the body of blowfish is designed to be as simple 
as possible to retain the desirable properties of cryptography structure. In algorithm 
design there are two basic ways to ensure that the key is long enough to ensure a 
ISRJournals and Publications
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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
 
particular security level. One is to design algorithm carefully so that the entire input to 
be preserved. The other is to design the algorithm with so many key bits that attacks to 
reduce the effective key length. 
The sub key generation process is designed to preserve the entire inputs of the key 
and distribute equally to all the sub keys. It also reduces the storage requirements. The 
448 limit on the key size ensures that every bit of every sub key depends on every bit of 
the key. 
Assume that the key bits are not repeated, but instead padded with zeros to extend it 
to the length of P- array. An attacker might find two keys that differ only in 64 bit 
value XOR ed with P1 and P2 known as sub keys produce the same encrypted value. If 
so he can find two keys that produce all the same sub keys. This is highly tempting 
attack for a malicious key generator. To prevent this attack the key bits are XOR ed 
repeatedly with Pi in the initial P- array. A total 522 iterations required to test a single 
key. 
CONCLUSION 
Secret key cryptography is older one and it contains only one key on both sides for 
encryption and decryption based on Data encryption standards. Blow fish algorithm is 
one of the best block cipher technique for large amount of data blocks. In this research 
we studies deeply about the blow fish algorithm and its operation. Also studied how 
the create sub keys with the help of permutation and substitutions. 
REFERENCES: 
[1] B. Schneier, Applied Cryptography, John Wiley & Sons, New York, 1994. 
[2] B. Schneier, Description of a New Variable-Length Key, 64-Bit Block Cipher
(Blowfish) 
[3] Fast Software Encryption, Cambridge Security Workshop Proceedings (December
1993), Springer-Verlag, 1994, pp. 191-204. 
[4] Yonatan Aumann, Yan Zong Ding, and Michael O. Rabin. Everlasting security in
the bounded storage model. IEEE Transactions on Information Theory,
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ISRJournals and Publications
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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
 
[5] Akavia, S. Goldwasser, and V. Vaikuntanathan. Simultaneous hardcore bits and
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Cryptography— TCC 2009, volume 5444 of Lecture Notes in Computer Science.
Springer-Verlag, 2009. 
[6] Steven M. Bellovin and Michael Merritt. Augmented encrypted key exchange: A
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[7] Eli Biham and Adi Shamir. Differential fault analysis of secret key cryptosystems.
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