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Logon with Digital Siganture (PKI/OCES - or what else they're called)

P: n/a
Hi everyone

Has anyone got the least experience in integrating the Digital Signature
with an ASP.NET[C#] Web Application?

Here in Denmark, as I supose in many other countries, they're promoting the
digital signature. A lot of people already has one, to do their taxes, and
much more. I have to use for a business-to-business e-commerce solution,
where it's vital that the right user is being logged on, and not give his
username and password to a colleague...

Due to the Digital Signatures usage, companies are very aware of which
employees has access to tax, VAT and things like that - and I can make a
more secure web application...

Anyone with just a good idea, own experiences, good links, or something?

Thanks.

Best Regards

Martin HN
Nov 17 '05 #1
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2 Replies


P: n/a
Hi, Martin,

We are currenly using this in an aplication, it works fine and is very easy
to use. This link will help you:

http://support.microsoft.com/default...;EN-US;Q315588

Regards - Octavio

"Martin Høst Normark" <mh*@jydepost.dk> escribió en el mensaje
news:43***********************@news.sunsite.dk...
Hi everyone

Has anyone got the least experience in integrating the Digital Signature
with an ASP.NET[C#] Web Application?

Here in Denmark, as I supose in many other countries, they're promoting
the digital signature. A lot of people already has one, to do their taxes,
and much more. I have to use for a business-to-business e-commerce
solution, where it's vital that the right user is being logged on, and not
give his username and password to a colleague...

Due to the Digital Signatures usage, companies are very aware of which
employees has access to tax, VAT and things like that - and I can make a
more secure web application...

Anyone with just a good idea, own experiences, good links, or something?

Thanks.

Best Regards

Martin HN

Nov 17 '05 #2

P: n/a
Martin Høst Normark wrote:
Hi everyone

Has anyone got the least experience in integrating the Digital Signature
with an ASP.NET[C#] Web Application?

Here in Denmark, as I supose in many other countries, they're promoting the
digital signature. A lot of people already has one, to do their taxes, and
much more. I have to use for a business-to-business e-commerce solution,
where it's vital that the right user is being logged on, and not give his
username and password to a colleague...

Due to the Digital Signatures usage, companies are very aware of which
employees has access to tax, VAT and things like that - and I can make a
more secure web application...

Anyone with just a good idea, own experiences, good links, or something?


One of the issues has been confusing identification and authentication.

the basic technology is asymmetric key cryptography; what one key (of a
key-pair) encodes, the other key decodes (to differentiate from
symmetric key where the same key is used for encryption and
decryption).

there is business process defined called public key ... where one of
the key (of an asymmetric key pair) is defined as public and made
freely available and the other is identified as private and kept
confidential and never divulged.

there is a business process defined called digital signature ... where
the originator calculates the hash of a message/document and encodes it
with their private key resulting in something called a digital
signature. they then transmit the message/document along with the
digital signature. The recipient recalculates the hash on the received
message/document, decodes the digital signature with the
(corresponding) public key and compares the two hashes. If they are
equal, then the recipient can assume:

1) the message/document hasn't been modified since signing
2) "sommething you have" authentication, i.e. the originator had access
to and use of the private key.

Basically, recipients build up a trusted repository of public keys used
for verifying digital signatures.

Digital signatures have also been used to upgrade existing
shared-secret
http://www.garlic.com/~lynn/subpubkey.html#secret

where the public key is registered in lieu of a pin/password and
instead of matching pin/password, the public key is used to verify the
originator's digital signature.

the most world-wide pervasive authentication infrastructure is possibly
RADIUS (extensively used by ISPs and other organizations for integrated
administrative authentication, authorization, and accounting). This was
originally been password based infrastructure ... but has been upgraded
with other technologies, like registering public keys in place of
passwords ... and the method of authentication can be selected on an
account-by-account basis.
http://www.garlic.com/~lynn/subpubkey.html#radius

another widely deployed (originally password) authentication
infrastructure is KERBEROS ... originally developed as part of MIT's
project athean (my wife and I periodically did project athena
technology audits in the late 80s). You find KERBEROS integrated into
lots of distributed infrastructures like windows and most unix flavors.
Originally, the internet draft for upgrading KERBEROS to digital
signature verification PK-INIT ... specified simply registering public
keys in lieu of passwords.

Another business process related to digital sigantures and public keys
that evolved involves certification authorities (CAs), digital
certificates, and PKIs. The paradigm is analogous to the "letters of
credit" (or letters of introduction) from the sailing ship days. The
design point is the offline email environment from the early 80s, where
the recipient dials-up their local (electronic) post office, exchanges
email, and hangs up. They then may be faced with first-time
communication from complete stranger ... with no local information
about the stranger and no resources available for obtaining information
about the stranger.

The idea is that there are these things called trusted certification
authorities that certify information about strangers and create
digitally0signed digital certificates that contains the certified
information. Recipients (or relying parties) are expected to load the
public keys of certification authorities into their local trusted
public key repositories.

Now when a stranger signs a message/document, they can transmit the
message/document, their digital signature, and their digital
certificate. The recipient will (hopefully) have the public key of the
certification authority in their local trusted public key repository
.... and can verify the CA's digital signature on the digital
certificate. From this, the recipient can supposedly trust the
information in the digital certificate. The recipient retrieves the
stranger's public key (that has also been included in the digital
certificate) and verifies the stranger's digital signature. The
recipient now supposedly can use information about the stranger
included in the digital certificate to determine what to do next.

One of the issues in the early 90s, was the x.509 identity certificate
standard ... that also included something called the non-repudiation
bit.

Basically certification authorities were looking at increasing the
value of digital certificates that they were selling. First they were
advocating that x.509 identity digital certificates be included on all
digitally signed authentication events .... turning even the most
simple authentication operation into a heavy duty identification
operation (and not just simply limited to first time communication
between strangers that had no other way of finding information about
the other party ... either offline or online).

The other issue is that the certification authorities didn't
necessarily know at the time they were creating an x.509 identity
certificate ... exactly what information that all possible recipients
might be interested in. As a result there was some direction to include
enormous amount of personal information in these x.509 certificates
(grossly aggrevating the scenario of turning every trivial
authentication operation into a heavy duty identification operation).

Then there was the non-repudiation flag. This possibly was the result
of some semantic confustion where the term "digital signature" and the
term "human signature", both contain the word "signature". The
non-repudiation flag in a digital certificate supposedly met than the
digital signature effectively carried the weight of a human signature
.... i.e. human intent, read, understood, agrees, approves, and/or
authorizes what was digitally signed.
It eventually became obvious that the setting of a flag in a digital
certificate by a certification authority possibly months in the past
..... could not actual guarantee that a human has read, understood,
agrees, approves, and/or authorizes something. As a result, the
non-repudiation flag has become severely depreciated.

The other gap in the PKI protocol with respect to non-repudiation flag
was that there is nothing in standard PKI protocols that can proove
what specific digital certificate a person actually attached to any
specific message. Given that a person might have two different digital
certificates for the same public key ... one with the non-repudiation
flag and one w/o the non-repudiation flag, then (in theory) the
recipient need only be able to find and produce the digital certificate
with the non-repudation flag ... to demonstrate that what had been
digitally signed is bound by human signature and non-repudiation rules.
Again, after some real world experience, it quickly became evident that
such a scenario was outlandish.

Going into the mid-90s, some number of institutions were starting to
realize that x.509 identity certificates, grossly overloaded with
enormous amounts of personal information represented significant
privacy and liability issues. As a result, you started to see something
called relying-party-only certificates
http://www.garlic.com/~lynn/subpubkey.html#rpo

the first ones that I'm aware of were by a large german financial
institutioin.
The issue is that the institution places all the information about the
individual in an accessable database and the digital certificate is
purely loaded with the index pointer to the database entry and the
individual's public key. In turns out that it became trivial to proove
that relying-party-only digital certificates are redundant and
superfluous; in part because it violates the fundamental design point
originally used to justify PKI and digital certificates (the recipient
had no other way of obtaining information about the originating
entity). Given that the recipient has to use the database index to
access the database entry, by definition they already have all the
information that might be represented by a digital certificate.

In such situations, it is trivial to eliminate the redundant and
superfluous digital certificates and return to the original digital
signature authentication design ... using the information that the
recipient already has access to.
http://www.garlic.com/~lynn/subpubkey.html#certless

note that sometime after the original pk-init draft for Kerberos, it
was updated to add the possibility of supporting PKI-based operations
(as opposed to simple, straight-forward registrations of public keys in
lieu of password)
so that it would be possible for total strangers to logon to your
system
(as per the original design point justifying PKI, certification
authorities, and digital certificates).

As an aside ... there is further problem with trying to use digital
signatures for both authentication as well as indication of human
signatures involving intent, read, understood, agrees, approves, and/or
authorizes. I've refered to this as a dual-use attack/vulnerability.

Many of the digital signature authentication infrastructures involve
servers transmitting random data to the client for digital signing (as
a countermeasure to replay attacks). The client digitally signs the
random data (w/o ever having read, understood, agrees, approves, and/or
authorizes) and returns the digital signature. The issue is that an
attacker might include some valid transaction or contract in lieu of
random bits, the client then applies a digital signature to the
non-so-random bits ... and the attacker then uses the information and
digital signature as proof of a valid transaction/contract.

some number of past collected posts on electronic signature legislation
(my wife and I were brought in to help word smith the cal. electronic
signature and then the fed. electronic signature legislation),
non-repudiation, and human intent ... as well as common for
identification and authentication to be frequently confused
http://www.garlic.com/~lynn/subpubkey.html#signature

here are posts that describes two-factor authentication involving
a chipcard performing digital signature ("something you have"
authentication)
and a PIN ("something you know" authentication) ... where the entering
of the PIN can also be used as an indication of "human signature". The
scenario is that the chipcard calculating a digital signature has none
of the characteristics required for establishing human intent, read,
understood, agrees, approves, and/or authorizes. However, a certified
terminal can display a message that say "enter you PIN if you agree to
the transaction". The physical hitting of keys in response to a message
can be used to establish human intent (in addition to knowing the
correct PIN being used as a form of "two factor" authentication). The
interesting aspect is that it is the entering of the PIN that is the
basis for human signature and not the generation of a digital signature
(where possibly because the term "digital signature" and "human
signature" both contain the word "signature" that gives rise to
frequent confusion).
http://www.garlic.com/~lynn/aadsm21.htm#3 Is there any future for
smartcards?
http://www.garlic.com/~lynn/aadsm21.htm#5 Is there any future for
smartcards?
http://www.garlic.com/~lynn/aadsm21.htm#13 Contactless payments and the
security challenges

some past posts on digital signature dual-use attack
http://www.garlic.com/~lynn/2004i.html#17 New Method for Authenticated
Public Key Exchange without Digital Certificates
http://www.garlic.com/~lynn/2004i.html#21 New Method for Authenticated
Public Key Exchange without Digital Certificates
http://www.garlic.com/~lynn/aadsm17.htm#57 dual-use digital signature
vulnerability
http://www.garlic.com/~lynn/aadsm17.htm#59 dual-use digital signature
vulnerability
http://www.garlic.com/~lynn/aadsm18.htm#1 dual-use digital signature
vulnerability
http://www.garlic.com/~lynn/aadsm18.htm#2 dual-use digital signature
vulnerability
http://www.garlic.com/~lynn/aadsm18.htm#3 dual-use digital signature
vulnerability
http://www.garlic.com/~lynn/aadsm18.htm#56 two-factor authentication
problems
http://www.garlic.com/~lynn/aadsm19.htm#41 massive data theft at
MasterCard processor
http://www.garlic.com/~lynn/aadsm19.htm#43 massive data theft at
MasterCard processor
http://www.garlic.com/~lynn/aadsm20.htm#0 the limits of crypto and
authentication
http://www.garlic.com/~lynn/aadsm21.htm#5 Is there any future for
smartcards?
http://www.garlic.com/~lynn/aadsm21.htm#13 Contactless payments and the
security challenges
http://www.garlic.com/~lynn/2005.html#14 Using smart cards for signing
and authorization in applets
http://www.garlic.com/~lynn/2005b.html#56 [Lit.] Buffer overruns
http://www.garlic.com/~lynn/2005e.html#31 Public/Private key pair
protection on Windows
http://www.garlic.com/~lynn/2005g.html#46 Maximum RAM and ROM for
smartcards
http://www.garlic.com/~lynn/2005m.html#1 Creating certs for others
(without their private keys)
http://www.garlic.com/~lynn/2005m.html#11 Question about authentication
protocols
http://www.garlic.com/~lynn/2005o.html#3 The Chinese MD5 attack

Nov 17 '05 #3

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