passlib.hash.nthash - Windows’ NT-HASH

New in version 1.6.

Warning

This scheme is very weak, the md4 digest it is based on has been severely compromised for many years. It should be used for compatibility with existing systems; do not use in new code.

This class implements the NT-HASH algorithm, used by Microsoft Windows NT and successors to store user account passwords, supplanting the much weaker lmhash algorithm. This class can be used directly as follows:

>>> from passlib.hash import nthash

>>> # encrypt password
>>> h = nthash.encrypt("password")
>>> h
'8846f7eaee8fb117ad06bdd830b7586c'

>>> # verify password
>>> nthash.verify("password", h)
True
>>> nthash.verify("secret", h)
False

See also

the generic PasswordHash usage examples

Interface

class passlib.hash.nthash

This class implements the NT Password hash, and follows the Password Hash Interface.

It has no salt and a single fixed round.

The encrypt() and genconfig() methods accept no optional keywords.

Note that while this class outputs lower-case hexidecimal digests, it will accept upper-case digests as well.

Format & Algorithm

A nthash consists of 32 hexidecimal digits, which encode the digest. An example hash (of password) is 8846f7eaee8fb117ad06bdd830b7586c.

The digest is calculated by encoding the secret using UTF-16-LE, taking the md4 digest, and then encoding that as hexidecimal.

FreeBSD Variant

For cross-compatibility, FreeBSD’s crypt() supports storing NTHASH digests in a manner compatible with the Modular Crypt Format, to enable administrators to store user passwords in a manner compatible with the SMB/CIFS protocol. This is accomplished by assigning NTHASH digests the identifier $3$, and prepending the identifier to the normal (lowercase) NTHASH digest. An example digest (of password) is $3$$8846f7eaee8fb117ad06bdd830b7586c (note the doubled $$).

passlib.hash.bsd_nthash

This object supports FreeBSD’s representation of NTHASH (which is compatible with the Modular Crypt Format), and follows the Password Hash Interface.

It has no salt and a single fixed round.

The encrypt() and genconfig() methods accept no optional keywords.

Changed in version 1.6: This hash was named nthash under previous releases of Passlib.

Security Issues

This algorithm should be considered completely broken:

• It has no salt.
• The MD4 message digest has been severely compromised by collision and preimage attacks.
• Brute-force and pre-computed attacks exist targeting MD4 hashes in general, and the encoding used by NTHASH in particular.