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RE: Multi-Factor Authentication Concern
From: "Dave Lewis" <dlewis () security-connect com>
Date: Tue, 14 Aug 2007 14:59:36 -0600

Multi-factor authentication offers two or more "methods" to authenticate
a single entity/user accessing a system. For example, a key fob used in
tandem with secure login name and password; all provided by the
self-same single entity/user.

Multi-key authentication offers two or more "entities/users" with
complementary keys sharing similar properties to simultaneously access a
system where access can't be entrusted to a single entity/user. For
example, two people each with a key or each with a code that when used
together access sensitive areas or activate "warheads".

It really depends on how you choose to access a system and the nature of
the system. Don't confuse them as the same. They have different
purposes. For most network resources, I "trust" (and monitor) an
individual to operate within the confines of their permissions, but I
want to authenticate that it is truly that individual operating within
the permissions, hence, multi-factor authentication suffices.


-----Original Message-----
From: listbounce () securityfocus com [mailto:listbounce () securityfocus com]
On Behalf Of Justin Ross
Sent: Tuesday, August 14, 2007 12:17 PM
To: Jason Sewell; security-basics () securityfocus com
Subject: RE: Multi-Factor Authentication Concern

I'm sorry, I have to play devil's advocate and disagree.

Initially I wanted to agree that Multi-factor authentication did indeed
refer to the same person; However, I do not believe it to be the case
after I too, took it to the most basic level, reading the actual
definition of the words, which I included below as well as the
dictionary referred to. 

I do not believe Multi-factor Authentication necessarily refers to a
single user, nor even a living entity. For example, if multiple
handwriting experts, and a computer with handwriting analysis algorithm,
and a tarot card reader, as well random people on the street, all
confirmed the authenticity of a signed document by Abraham Lincoln,
would that not be Multiple-factor Authentication of that document? 

Why do nuclear submarines require multiple people with keys and codes to
press the launch button, and approval from the president? Is that not
Multi-factor authentication of not even individuals (who also pass
authentication checks to even get on the submarine) but a process (or
even multiple processes such as chain of command as well)? When you say
"as it is commonly defined", please cite where you are getting the
definition from? Isn't the point of this thread that you cannot cite one
and need help locating such a source? If you said "culturally defined by
the INFOSEC community", I would somewhat agree.

Really though, I think the answer hinges on the definition of the words
themselves, which doesn't necessarily indicate a person is involved (at
any point), let alone the single "same" person.

Just my 0.02.

Security Engineer

American Heritage Stedman's Medical Dictionary  
Many; much; multiple: multiarticular. 
More than one: multiparous. 
More than two: multipolar.

American Heritage Dictionary 
One who acts for someone else; an agent. 
A person or firm that accepts accounts receivable as security for
short-term loans. 
Mathematics One of two or more quantities that divides a given quantity
without a remainder. For example, 2 and 3 are factors of 6; a and b are
factors of ab. 
A quantity by which a stated quantity is multiplied or divided, so as to
indicate an increase or decrease in a measurement: The rate increased by
a factor of ten.  

American Heritage Dictionary 
To establish the authenticity of; prove genuine

-----Original Message-----
From: listbounce () securityfocus com [mailto:listbounce () securityfocus com]
On Behalf Of Jason Sewell
Sent: Tuesday, August 14, 2007 7:05 AM
To: security-basics () securityfocus com
Subject: Re: Multi-Factor Authentication Concern

I appreciate all of these responses.

The general consensus seems to be:

1) The system that "Bob" has implemented does not reflect multi- factor
authentication as it is commonly defined, and
2) there may be some esoteric reason to require different people to
provide different authentication factors to protect a single resource,
3) such a convoluted access control mechanism is not appropriate for
protection of our data center, and furthermore
4) accounting and logging are complicated by such a system.

However, what I still have not found yet is an authoritative document
that I can point to and say "Bob, you're wrong". He's a hard-headed guy
and responses from security experts on a mailing list won't convince
him. I looked at all of the suggested links, including the Wikipedia
article, and I cannot find anything that explicitly states that the
factors in a multi-factor authentication system must all be from the
same person.

So, I'll show him these response, and I'll continue to try to find an
authoritative source for my assertion (or perhaps I'll edit the
wikipedia article).

Thanks again everyone for you help!

On Aug 14, 2007, at 8:58 AM, Kevin Wilcox wrote:

Hash: SHA1

Mngadi, Simphiwe (SS) wrote:

All three are accountable; I don't see the logic in your hypothesis. 
in anyway authentication should be monitored, and your concern should

have been build-in into the security system.

All three *are* accountable and therein lies the problem - only
*one* of
the individuals actually entered the data centre but it appears as if 
all three of them entered. Authentication is not only a method for 
authorization, it is a method of accounting for who accessed what 
resources. Just because all three of them are authorized to be in the 
data centre doesn't mean that any one of them should be able to gain 
entry using the credentials of the other two. One of the things 
multi-factor authentication attempts to address is the scenario where 
an individual can pass themselves off as someone else - basically ID 

Another scenario would be on-line banking. Suppose you and your 
business partner have access to the same account. You decide to use 
web-based banking. To access the account information you have to login

using a password then enter a PIN. To gain access to the account 
details you would not login using your password then enter your 
partner's PIN - you would use *your* password and *your* PIN. Like the

data centre scenario, just because more than one person has access to 
a resource doesn't mean you allow authentication credentials from 
anyone with access - it destroys the concept of accountability. 
Instead you require that all of the authentication credentials come 
from the same person so you know who to hold accountable if something 
happens (and because it could be the law in your vicinity).

That said, there *are* times when group level access may be desired 
and a "piece of the key" from each person is acceptable (or required) 
- if that is the case then the original question is moot.

I hate relying on hypothetical examples but it really does come down 
to "what are you trying to accomplish with your authentication 
and "what are the laws in your area?". If group accountability is your

goal then you can suffice with allowing credentials from anyone at any

stage in the process (just make sure you have other accountability 
measures in place). If you want granular accountability at the 
individual level then all of the credentials must come from the same 

I hope that helps.

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