Re: ** Statement Summary #7 - Final

[carl@xxxxxxxxx (Carl Hage)]

>From clueder@mail06.mitre.org  Mon Feb 26 09:14:36 1996
>> and Carl comments:
>>All digital signatures provide both authentication, non-repudiation
>>of origin, and integrity.
>
>I think you are oversimplifying this, or assuming that public keys are used.

Sorry, I'm assuming public keys are used. All the digital signature
algorithms that I know of use public keys.

>You can provide integrity and authentication of origin without providing 
>non-repudiation of origin, by using DES (Data Encryption Standard) Secret key 
>to encrypt the token.

DES only provides privacy. There is no integrity check, since DES decryption
alone doesn't protect against errors. It doesn't authenticate the origin,
since someone within your company could send a forged message to
itself.

> That does not constitute a signature. Why would you do 
>that? Because DES is simple to implement, free, fast algorithm, keys are 
>trivial to generate, and you don't need a supporting infrastructure (just 
>exchange a secret key with each trading partner). And it has never been 
>broken,

But secret keys are easily stolen. With a hardware encryption card,
the private keys are buried in a chip and can't be extracted, even by
people who posess the card.

> which is more than can be said for the private key approaches (the 
>Internet was used to factor a large public key into its two prime numbers in 
>just seven months, or less--I forget).

Actually, that was a small key (much smaller than the keys normally used).
The export laws greatly reduce the length of the keys so that the NSA
can break them. Of course such a key can be broken, since that's the
purpose of the length limit.

To get around the export restrictions, the key used to sign can be
longer than the key used to encrypt for privacy.

One important feature of public keys, is that the certificate process
can be used to authenticate an arbitrary signature. This will be critical
in Electronic Commerce, where retail stores do business on the net.

Actually, MOSS (from tis.com) is free for email-only use.

At the Email/WWW Internet expo in San Jose last week, the US Post Office
was there and said they will be issuing X.509 certificates starting
(or announcing?) in April. That should make certificates easy to get.
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Carl Hage                                              C. Hage Associates
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<http://www.chage.com/chage/>                          Sunnyvale, CA 94086