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List:       ms-cryptoapi
Subject:    Re: signing under SP4
From:       Jeff Spelman <jeffspel () MICROSOFT ! COM>
Date:       1999-05-27 23:37:55
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Guy
   If you are using the same key and the same hash value every time then the
RSA signature should be the same, note that this is not true for a DSS
signature, I didn't see where you mentioned the signature algorithm you are
using.  This will be true of RSA signatures on Win9x, NT4 (all SPs) and
Windows 2000.
Thanks Jeff

-----Original Message-----
From: Guy Dumais [mailto:guy_dumais@SILANIS.COM]
Sent: Thursday, May 27, 1999 12:09 PM
To: CryptoAPI@DISCUSS.MICROSOFT.COM
Subject: signing under SP4


Hi,
        I have an application that works fine under
NT 4.0 SP 3.  After installing SP 4,  some problems
appeared.

It appears that the encryption of a given hash is not
always the same even though the signature key is the
same.

Here are the calls that are made where Digest contains
some fixed value and SigKeyData is an unencrypted
private key blob.

        CryptSetHashParam(hHash, HP_HASHVAL, Digest, 0);

        CryptImportKey(hProv, SigKeyData, DataLen, 0, CRYPT_EXPORTABLE,
&hSignatureKey);

        CryptSignHash(hHash, AT_SIGNATURE, NULL, 0, DigSig, &SigLen);

Several executions of these lines will give different values
for DigSig.
The problem only appears under SP 4 and probably SP 5
also.  Is there some key parameters that must be set
before using it to sign the hash?

Any hint would be greatly appreciated.

Guy Dumais
Silanis Technology
mailto:guy_dumais@silanis.com

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