Blowfish is a variable-length, a new secret-key block cipher. The research paper says that Blowfish is a Feistal network, iterating a simple encryption function 16 times. Its main features as mentioned in the research abstract are :
- Block cipher: 64-bit block.
- Variable key length: 32 bits to 488 bits.
- Much faster than IDEA and DES.
- Unpatented and royalty free.
- No license required.
About Blowfish: The research paper Cryptography Blow fish Information Technology Seminar explains what Blowfish is. The Blowfish algorithm consists of: a key-expansion part and a data- encryption part. Key expansion converts a variable-length key of at most 56 bytes (448 bits) into several sub key arrays totaling 4168 bytes. Data encryption occurs via a 16-round Feistel network. Each round consists of a key-dependent permutation, and a key- and data-dependent substitution. The additional operations are four indexed array data lookups per round. Implementations of Blowfish that require the fastest speeds should unroll the loop and ensure that all sub keys are stored in cache.
The research paper suggests that a standard encryption algorithm must be implementable on a variety of different platforms, each with their own requirements.
These include:
Special hardware: The algorithm should be efficiently implementable in custom VLSI hardware.
Large processors: The algorithm should be efficient on 32-bit microprocessors with 4 KB program and data caches.
Medium-size processors: The algorithm should run on micro controllers and other medium-size processors, such as the 68HC11.
Small processors: It should be possible to implement the algorithm on smart cards.
The requirements for small processors are the most difficult. RAM and ROM limitations are severe for this platform. Also, efficiency is more important on these small machines.
Conclusion: The research paper ends on a conclusion describing in nutshell the functions of Blowfish. In this paper it was discussed that Blowfish, is a variable-length key block cipher. Blowfish is only suitable for applications where the key does not change often, like a communications’ link or an automatic file encryptor.
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