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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
 
DESCRIPTION: 
Blow fish is a variable length key containing 64 bit block cipher. Each round depends on 
key permutation and a key data dependent substitution. All operations are XOR’s and 
additions on 32 bit words. The only additional operations are four indexed array data 
lookups per round.
 
SUB KEYS; 
 
Blow fish uses a large number of subkeys. There keys must be pre computed before data 
encryption. 
The P-array consists of 18 32 bit sub keys. 
P1, P2, P3, . . . . . . P18. 
There are 4 32 bit S-boxes with 256 entries each 
S1,0, 
S1,1, 
S1,255; 
S2,0 
S2,2, 
S2,255; 
S3,0 
S3,1, 
S3,255; 
S4,0 
S4,1 
S4,255; 
ENCRYPTION: 
Blowfish has 16 rounds 
The input is a 64 bit data element, 
d
Divide i into two 32 bit halves : dL and dR 
Then for i=1 to 16; 
dL= dL XOR Pi 
dR = F(dL) XOR dR 
Swap dL and dR 
ISRJournals and Publications
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