Improving security of password (passphrase) based auth schemes  (MD5 proposal)
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Introduction
------------

Currently the RIPE Database implements the only password based "auth"
scheme, which is "CRYPT-PW" scheme.  This scheme uses an encryption process
which is similar to that used to make and check login passwords in UNIX.

A password is chosen by the user; this is encrypted using DEC crypt(3) and
put in the database. The encrypted password can be seen by everyone. The
user sends the clear password in the same mail as the request to change an
object using "password:" pseudo-attribute.

Motivation
----------

The main flaw of the CRYPT-PW scheme is that password is limited to 8
characters, which makes exhaustive searches of the key space possible given
that crypted password is publicly available. Also the DES algorithm itself
has a few quirks which lower the security of the scheme.

Allowing longer keys and using more secure encryption algorithm could
improve security of password-based auth scheme.

Proposal
--------

A new "auth:" scheme is introduced based on MD5 hash algorithm. The format
of the new "auth" scheme is:

auth:             MD5-PW <digest>

where <digest> is a 128-bit MD5 digest.

For example: 

auth:             MD5-PW 4aabd3dbc0746c8a4b5467f99a4f8524

When submitting an update to the database that needs to be authorised using
this scheme, a "password:" pseudo-attribute must be used to submit a key
(passphrase). Line continuation is not allowed for this attribute, so the
whole key should fit on one line. If the key gets split across multiple
lines this will be treated as syntax error.

If the mntner that defines authorisation information for the submission has
CRYPT-PW and MD5-PW "auth" schemes, the key specified by "password:" will be
checked for both types.