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Blowfish cryptography software

Blowfish is a block cipher algorithm devised by Bruce Schneier and detailed in his book Applied Cryptography Protocols, Algorithms, and Source Code in C, 2nd edition, Wiley, 1996. The source code is available in several languages, including a Visual Basic version by the author of CryptoSys, David Ireland.

Blowfish uses a 64-bit block and a variable key up to 448 bits long. It is efficient and secure.

Blowfish functions available in CryptoSys API

BLF_Hex - en/decrypt a hex string in one step
BLF_HexMode - en/decrypt a hex string in one step using specified mode (EBC, CBC, CFP, OFB, CTR)
BLF_Bytes - en/decrypt a byte array in one step
BLF_BytesMode - en/decrypt a byte array in one step using specified mode (EBC, CBC, CFP, OFB, CTR)
BLF_File - en/decrypt a file
BLF_FileHex - en/decrypt a file using a hex key
BLF_Init - initialise the context ready for repeated use
BLF_InitHex - initialise the context using hex values ready for repeated use
BLF_Update - en/decrypt the next set of data and update the context
BLF_UpdateHex - en/decrypt the next set of data in hex and update the context
BLF_Final - close and clear the context

See the Blowfish Class for the equivalent .NET methods for C# and VB.NET/2005/8.

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This page last updated 15 August 2025.