ParallelHash256

What is ParallelHash256?

ParallelHash256 is a SHA-3-derived hash function designed to hash long messages by splitting them into fixed-size byte blocks. It is based on cSHAKE256 and standardized in NIST SP 800-185. This calculator reads text, a local file, or a file URL and returns the requested output length in the selected encoding. Identical input bytes, block size, customization string, and output length produce the same value.

How to use this hash calculator

Choose Text, Local File, or File URL as the source. For text, select the input encoding. Set Block Size (B) as a byte count, the output length, and an optional Customization string for domain separation. Use Hex when comparing technical test vectors, or Base64 when a compact text representation is more convenient.

Result example

With UTF-8 abc, block size 8 bytes, empty customization, and a 512-bit output, ParallelHash256 is ba9950afef636b66d6caad0f573f15c45db78bde25a96606c87fce188ce0f0715abda5377018277c4a86228f4bd5cf72dfe81dc1cdde1fbb022fac9b27de086d in Hex. Changing the block size or customization changes the digest without changing the message.

Important limitations

ParallelHash is unkeyed, so a customization string provides domain separation rather than authentication. Use KMAC256 when a secret key and message authentication are required. Different block sizes produce unrelated digests for the same message. This browser implementation processes blocks sequentially; the ParallelHash construction still allows parallel implementations elsewhere.

Use ParallelHashXOF256 when the application requires the extendable-output form rather than committing the requested length inside the ordinary ParallelHash computation.

Frequently asked questions

Why does my result differ from another tool?

Check the exact input bytes, Block Size (B) in bytes, customization string, and output length. ParallelHash256 and ParallelHashXOF256 encode output length differently and are not interchangeable.

Can I use the result to verify data?

Yes, if every parameter is defined by the protocol and the expected value is trusted. Matching an untrusted digest copied from the same location does not establish authenticity.