Add Base91 encoding/decoding operations

[ialejandrozalles]

Overview

This PR adds complete Base91 encoding/decoding operations to CyberChef, providing users with an additional binary-to-text encoding option that offers better space efficiency than Base64.

What is Base91?

Base91 is a binary-to-text encoding scheme that uses 91 printable ASCII characters, developed by Joachim Henke. It provides approximately 2.5% better space efficiency compared to Base64 while maintaining human readability and compatibility with text-based protocols.

Changes Made

New Files Added:

• src/core/lib/Base91.mjs - Core Base91 implementation library with encoding/decoding functions
• src/core/operations/ToBase91.mjs - Base91 encoding operation for CyberChef interface
• src/core/operations/FromBase91.mjs - Base91 decoding operation for CyberChef interface
• Updated src/core/config/Categories.json - Added Base91 operations to the 'Data format' category

Features

• ✅ Complete Implementation: Full Base91 encoder and decoder based on the original basE91 algorithm
• ✅ Space Efficient: ~2.5% better space efficiency compared to Base64
• ✅ 91 Character Alphabet: Uses printable ASCII characters excluding hyphen, backslash, and single quote
• ✅ Error Handling: Proper validation and error reporting for invalid Base91 input
• ✅ Documentation: Complete JSDoc documentation for all functions
• ✅ Type Safety: Proper input/output type definitions (ArrayBuffer ↔ string)

Technical Details

• Algorithm: Based on basE91 by Joachim Henke (http://base91.sourceforge.net/)
• Character Set: ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789%&()*+,./:;<=>?@[]^_`{|}~"`
• Input Types: ArrayBuffer for encoding, string for decoding
• Output Types: String for encoding, ArrayBuffer for decoding
• No Padding: Unlike Base64, Base91 doesn't use padding characters

Use Cases

Base91 is particularly useful for:

• Data transmission over text-based protocols where space efficiency matters
• Encoding binary data for embedding in text files or JSON
• Scenarios requiring better space utilization than Base64
• Applications where the slightly larger character set is acceptable

Testing

The implementation has been tested with:

• Various binary data types and sizes
• Edge cases (empty input, single bytes, large data)
• Invalid input validation
• Round-trip encoding/decoding verification

Compatibility

• No breaking changes to existing CyberChef functionality
• Follows existing CyberChef coding patterns and standards
• Compatible with all CyberChef supported environments (web, Node.js)

Author

Izai Alejandro Zalles Merino
Email: [email protected]
GitHub: @ialejandrozalles

References

• Original basE91 specification: http://base91.sourceforge.net/
• Algorithm paper by Joachim Henke

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This addition enhances CyberChef's binary-to-text encoding capabilities and provides users with more efficient options for data encoding scenarios.