Problems with Example 5.1.

It has been reported to me that OpenSSL has problems verifying the
signature on example 5.1.

I have now analysed the example and found a few issues.

Firstly the description:

> A SignedData with no attribute certificates, signed by Alice using
> DH-DSS, just her certificate (not Carl's root cert), no CRL. The
> message is ExContent, and is included in the eContent. There are no
> signed or unsigned attributes.
> 

DH-DSS??

The final OCTET STRING which encapsulates the signature includes a
trailing zero.

Finally I cannot get OpenSSL to verify the signature on that example.
OpenSSL does however verify the signature on the certificate.

I didn't immediately report this because I could not be certain there
wasn't a bug in OpenSSLs DSA implementation that this example triggered.

I have since manually implemented the DSA verification algorithm for
this example using the Unix 'dc' calculator and input the relevant
values.

The result from dc agrees with OpenSSL: that is the value for 'v' is
identical (see FIPS186 section 6) not just the fact that it cannot
verify the signature.

While I cannot rule out the possibility that I've done something silly
the evidence suggests there is a problem with that signature.

Steve.
-- 
Dr Stephen N. Henson.   http://www.drh-consultancy.demon.co.uk/
Personal Email: [email protected] 
Senior crypto engineer, Celo Communications: http://www.celocom.com/
Core developer of the   OpenSSL project: http://www.openssl.org/
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