Add RC6 Encrypt and RC6 Decrypt operations

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This PR implements RC6 encryption and decryption operations for CyberChef, addressing the request for RC6 cipher support.

Implementation Details

RC6 Cipher Algorithm:

• Complete implementation of the RC6 block cipher from scratch following the specification
• 128-bit block size with variable key lengths (128, 192, 256 bits supported)
• 20-round encryption/decryption with proper key expansion
• Support for both CBC and ECB modes with PKCS#7 padding

New Operations:

• RC6 Encrypt: Encrypts data using the RC6 algorithm

  • Key input formats: Hex, UTF8, Latin1, Base64
  • IV input formats: Hex, UTF8, Latin1, Base64 (for CBC mode)
  • Modes: CBC, ECB
  • Input formats: Raw, Hex
  • Output formats: Hex, Raw, Base64

• RC6 Decrypt: Decrypts RC6-encrypted data

  • Key input formats: Hex, UTF8, Latin1, Base64
  • IV input formats: Hex, UTF8, Latin1, Base64 (for CBC mode)
  • Modes: CBC, ECB
  • Input formats: Hex, Raw, Base64
  • Output formats: Raw, Hex

Files Added/Modified:

• src/core/lib/RC6.mjs - Core RC6 cipher implementation
• src/core/operations/RC6Encrypt.mjs - RC6 encryption operation
• src/core/operations/RC6Decrypt.mjs - RC6 decryption operation
• src/core/config/Categories.json - Added RC6 operations to "Encryption / Encoding" category
• tests/operations/tests/RC6.mjs - Comprehensive test cases for both operations

Example Usage:

Input: "Hello, World!"
Key (Hex): "000102030405060708090a0b0c0d0e0f"
Mode: ECB
Output (Hex): "8c70b5eac2518728f7e3bf5842d080b5"

The implementation follows CyberChef patterns and integrates seamlessly with the existing operation framework. All encryption/decryption operations support round-trip verification and handle various input/output formats as expected by users.

Note: Since RC6 is not available in standard crypto libraries like node-forge or crypto-js, this implementation provides a complete, standalone RC6 cipher following the official specification.

Fixes #1.

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• googlechromelabs.github.io
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