Blowfish Encryption

Overview

Blowfish is a block cipher that was designed in 1993 by Bruce Schneier as a fast, free alternative to existing encryption algorithms. Like Skipjack it can be used as a convenient and much faster substitute for DES. Since then Blowfish has been extensively analyzed and no significant weaknesses have been found. It is considered to be a strong algorithm and has been implemented in over 130 commercial applications. Bruce Schneier was also one of the designers of the Twofish algorithm, which is one of the five finalists selected by NIST in the Advanced Encryption Standard (AES) competition. Twofish was developed as a successor to the Blowfish cipher, which does not meet the design requirements of the AES.

In Depth

Blowfish is a 64-bit block cipher, meaning that data is encrypted and decrypted in 64-bit chunks. The key length can vary from 32 to 448 bits. The algorithm uses 16 rounds, or iterations of the main algorithm. It has been found that the number of rounds is exponentially proportional to the amount of time required to find a key using a brute-force attack. So as the number of rounds increases, the security of the algorithm increases exponentially.

Private Encryptor's implementation of Blowfish allows the key to vary from 32 to 448 bits, as per the algorithm specification. Some early implementations of Blowfish contained a subtle bug that allowed the algorithm to be easily broken on a standard Pentium class PC. This bug has been fixed in Private Encryptor's implementation.

The detailed description of the Blowfish algorithm is contained in the original Blowfish paper, written by Bruce Schneier, which was presented at the First Fast Software Encryption workshop in Cambridge. The paper is rather technical and a certain degree of mathematical proficiency is required of the reader in order to understand it. For anyone who wishes to write their own implementation of Blowfish, you can get the S-Boxes by clicking here.

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