KMACXOF128
Calculate KMACXOF128 output for text, local files, or URLs using a secret key, customization string, selectable input encoding, and output length. Expand to read more.
What is KMACXOF128?
KMACXOF128 is a keyed extendable-output function based on Keccak and cSHAKE128. Unlike KMAC128, its internal encoding does not commit to a fixed output length before output begins. It accepts a secret key, input message, requested output length, and optional customization string. This calculator reads text, a local file, or a file URL and returns the requested KMACXOF output in the selected encoding. Identical input bytes, key, customization string, and output length produce the same result.
How to use this KMACXOF calculator
Enter text, choose a local file, or provide a URL. Select the input encoding for text, output encoding, output length, secret key, and optional customization string, then calculate the result. Local files are processed in your browser and are not uploaded by this tool. Use Hex when comparing technical test vectors, or Base64 when a compact text representation is more convenient.
Result example
For repeatable results, the visible text and its byte encoding must match. For example, UTF-8 text and a Hex string that represents those same bytes produce the same KMACXOF128 result when their input types are selected correctly. Two files produce the same value only when their bytes and all selected parameters are identical.
Important limitations
KMACXOF does not encrypt or hide the input. Its output can be used as a message authentication code or pseudorandom function output when applied according to the relevant protocol. Verification is meaningful only when the key remains secret and comes from an appropriate source. The key, customization string, output length, input bytes, and encoding must all match; do not compare the result with ordinary KMAC, SHA-3, or SHAKE output.
KMACXOF is specified in NIST SP 800-185.
Frequently asked questions
Why does my result differ from another tool?
Check the exact input bytes, character encoding, line endings, output format, and every algorithm-specific option. Displayed text that looks identical can contain different bytes. Also confirm that the other tool uses KMACXOF128 rather than KMAC128.
Can I use the result to verify data?
Yes, when you recompute it with the same secret key and parameters. Matching output can detect modification by someone who does not know the key; publishing that key removes this authentication property.
