OMBLOWFISH is a low-level OmniMark interface to the Blowfish cryptographic algorithm. The Blowfish encryption algorithm is described in [1] Bruce Schneier, ``Description of a New Variable-Length Key, 64-bit Block Cipher (Blowfish)'', Fast Software Encryption, Cambridge Security Workshop, p. 191--204, December 09--11, 1993.

The library provides functions for encoding and decoding 64-bit quantities using an encryption key. These 64-bit quantities are represented as OmniMark strings with a length of eight characters. An input string longer than eight characters is rejected; an input string shorter than eight characters is padded to a length of eight characters using null bytes.

A more convenient interface to the Blowfish algorithm is provided by the OMFFBLOWFISH library, which provides filter functions for encrypting and decrypting data in a streaming fashion. It, in turn, uses this library for its low-level implementation.

The OMBLOWFISH library provides three external functions and one external data type; it also provides one conversion function as a convenience.

• state is an external data type that represents the state of a decryption or encryption calculation.
• decode is an external function that takes a 64-bit quantity and a state, and returns the decrypted value as a 64-bit quantity, encased as a string.
• encode is an external function that takes a 64-bit quantity and a state, and returns the encrypted value as a 64-bit quantity, encased as a string
• set-encryption-key takes an encryption key as a string and a state, and initializes the state using the encryption key.

The conversion function provided by OMBLOWFISH takes a string and returns a fully-initialized state. This can be convenient when initializing a local state.

Requirements

To use OMBLOWFISH in your OmniMark program, you must import it into your program using a statement like this:

     import "omblowfish.xmd" prefixed by blowfish.

OMBLOWFISH Generated Exceptions

This is a complete list of the OMBLOWFISH library external exceptions that may be thrown back to the calling OmniMark program. These are all catchable using the #external-exception label.

• OMBLOWFISH_001 Unable to allocate encryption state.
• OMBLOWFISH_101 The Blowfish state is not initialized.
• OMBLOWFISH_102 The length of the input string cannot exceed eight characters.
• OMBLOWFISH_103 The length of the input string cannot be zero.

Functions blowfish.decode blowfish.encode blowfish.set-encryption-key blowfish.state

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