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List:       ms-cryptoapi
Subject:    Re: how to do rsa private encrypt (rsa sign) using MSCAPI (ie
From:       John Banes <jbanes () WINDOWS ! MICROSOFT ! COM>
Date:       2001-11-16 1:02:21
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The CryptHashData does not support the CALG_SSL3_SHAMD5 algorithm type.
Instead, you need to use CryptSetHashParam with HP_HASHVAL to set the
36-bit hash value prior to performing the signature operation.

Regards, John

-----Original Message-----
From: Aslam [mailto:aslam@FUNK.COM] 
Sent: Thursday, November 15, 2001 1:26 PM
To: CryptoAPI@DISCUSS.MICROSOFT.COM
Subject: how to do rsa private encrypt (rsa sign) using MSCAPI (ie using
C ALG_SSL3_SHAMD5 in CryptCreateHash())...??


Hi,

Has any one used the CALG_SSL3_SHAMD5 in CryptCreateHash().. What I need
is that I should be able to perform RSA_private_encrypt operation using
microsoft crypto api so that I can use that for preparing
certificate_verify message of ssl/tls specification. For that I do  the
following:

HCRYPTPROV    hCryptProv = 0;
HCRYPTHAS       hCryptHash = 0;

// acquire the desired context
if(! CryptAcquireContext(&hCryptProv, 0, "Microsoft RSA SChannel
Cryptographic Provider", PROV_RSA_SCHANNEL, 0)) {
    PrintErrorMessage(GetLastError());
    goto error;
}

// create the hash object
if(! CryptCreateHash(hCryptProv, CALG_SSL3_SHAMD5, 0, 0, &hCryptHash)) {
     PrintErrorMessage(GetLastError());
     goto error;
}

// perform hash (md5+sha1 for ssl/tls)
if(! CryptHashData(hCryptHash, pIn, nIn, 0))
{
    PrintErrorMessage(GetLastError());
    goto error;
}


// get the required buffer size
if(! CryptSignHash(hCryptHash, dwKeySpec, 0, CRYPT_NOHASHOID, 0,
&dwSignedDataSize))
{
    PrintErrorMessage(GetLastError());
    goto error;
}

// alloc required buffer
pSignedData = new unsigned char(dwSignedDataSize);

// perform private encrypt
if(! CryptSignHash(hCryptHash, AT_SIGNATURE, 0, CRYPT_NOHASHOID,
pSignedData, &dwSignedDataSize)) {
    PrintErrorMessage(GetLastError());
    goto error;
}

But I'm getiing a failure at CryptHasData() with following error code:
0x80090008 => Invalid algorithm specified.

Does any one tell me why.. or any other way to perform RSA private
encrypt using cryptoapi..

Thanks
Aslam

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