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SFL bug with 512-bit DSA Certificates



We have encountered a problem with SFL processing some DSA Certificates, which are attached in a PKCSœ12 file whose password is password. John Stark has produced the following analysis.

1. The DSA certificates that cause the "Montgomery" error have 512-bit 
keys, whereas our own have 1024-bit keys.

2. The error is reported because SFL, including the common "CTIL 
manager" library and the "sm_free3 CTIL" library that interfaces to 
crypto++ (though not crypto++ itself) has burnt-in assumptions that DSA 
keys are 1024-bit.  I have found this in a number of places in the code. 
  There are one or two places that do realise that DSA keys can be 
smaller, but many more that don't.

3. I confirmed this by putting debug printfs in the crypto++ routine 
that reports the error, and determining that it is passed 64 bytes of 
modulus rather than 32 (in native byte order, i.e. reversed from the 
ASN.1), the first 32 of which are garbage, mostly zero, and the 2nd 32 
of which are those from the ASN.1.

4. The 512-bit DSA keys and certificates work correctly when used with Microsoft CryptoAPI.



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Attachment: TestCerts.pfx
Description: application/ftbp.1.2.840.1.113694.2.2.1.1