MD4 Hash Generator

What the MD4 generator does

This produces the MD4 hash of your text, a 32-character hex fingerprint. Type or paste your text, press Convert, and copy or download the result. MD4 is mostly of historical interest now, but it is a genuinely important piece of history, and like MD5 it cannot be reversed back into your text.

It runs in your browser, so nothing you enter is uploaded.

How to use it

1. Enter your text. Type or paste it, or upload a plain text file.
2. Press Convert. The 32-character MD4 hash appears, ready to Copy or Download.

The grandparent of modern hashes

MD4 was designed by Ronald Rivest in 1990, and it matters far more than its age suggests, because almost every hash that came after borrowed from it. MD5 was built as a more careful MD4. SHA-1 and the SHA-2 family carry its design ideas forward too. So when you read on the SHA-256 or MD5 pages about how these hashes work, you are really reading about a lineage that starts here. MD4 produces the same 128-bit, 32-character fingerprint that MD5 does, and it was built to be very fast.

Thoroughly broken, and retired

That speed came at a cost, and MD4 is broken even more completely than MD5. Collisions, two inputs sharing a hash, can now be produced about as quickly as a hash can be checked, a matter of microseconds, and even the harder problem of working back from a hash to a matching input has been cracked for it. The standards bodies retired it long ago: the document that first described MD4 was formally moved to historic, obsolete status. There is no scenario today where you should choose MD4 for security. It lives on this site for completeness and for matching old systems, not for protecting anything. If you need a secure hash, the SHA-256 page is where to go.

Where you still bump into it

Despite all that, MD4 did not vanish, because it was baked into some long-lived systems before its flaws were understood. The most notable is Microsoft Windows, where the old password hash, the one often called the NT hash, is simply MD4 of the password. It also turns up in the file-fingerprinting of tools like rsync and some older peer-to-peer networks. So if you are poking at a legacy login system or an old protocol and you see MD4, this tool lets you reproduce what it produces. Just remember that finding MD4 in a system today is usually a sign of its age, not its safety.

The library doing the work

The hashing is handled by js-md4, a small JavaScript implementation of MD4. Your text is read as bytes and run through the algorithm in your browser, with the 32-character hex result handed back.

Questions people ask

Is MD4 safe to use?

No. It is even more thoroughly broken than MD5, with collisions producible in microseconds. It should never be used for security, only for historical interest or matching old systems.

Is the Windows NT password hash really MD4?

Yes. The classic NT hash is MD4 applied to the password, which is one of the main reasons MD4 still appears in tools today despite being obsolete.

Can I reverse an MD4 hash?

No. Like every hash in this family it is one-way, so the original text cannot be recovered. The MD5 page explains why, and why "decrypt" tools only work for guessable inputs.

References

1. Rivest, R. (1992). RFC 1320: The MD4 Message-Digest Algorithm. Internet Engineering Task Force (IETF). https://www.rfc-editor.org/rfc/rfc1320
2. Turner, S., Chen, L. (2011). RFC 6150: MD4 to Historic Status. Internet Engineering Task Force (IETF). https://www.rfc-editor.org/rfc/rfc6150
3. js-md4, an MD4 implementation for JavaScript (npm package). https://www.npmjs.com/package/js-md4