CryptExportKey 3DES Key...

[TemporalBeing]

I am working to try to export a 3DES key to be used as a template, and
am getting the NTE_BAD_KEY error during the export. I know the docs say
that this means that either of the "hkey and hexpkey" are invalid -
however, I just generated the key in the same context and the handle is
what was just given to me by CryptGenKey:

...
HCRYPTPROV Win32_RSA_Enhanced_Provider = NULL;
if(!CryptAcquireContext(&Win32_RSA_Enhanced_Provider,"MyContext",MS_ENHANCED_PROV,PROV_RSA_FULL,0))

return;
...
HCRYPTKEY Win32_3DES_Key = NULL;
if
(!CryptGenKey(Win32_Provider,CALG_3DES,CRYPT_EXPORTABLE,&Win32_3DES_Key))

return;
...
//Try to get the size of the private key blob
DWORD DataSize = 0;
CryptExportKey(Win32_3DES_Key,NULL,PRIVATEKEYBLOB,0,NULL,&DataSize);
DWORD Last_Error = GetLastError();
//Last_Error = 0x80090003 = "Bad Key."

According to the docs, the MS_ENHANCED_PROV should allow the 3DES key
to be exported without having a key to encrypt it.

The calls are set up in different functions - wrapped - but I have the
same code working just fine for AT_EXCHANGE, DH_EPHEM, and DH_PREGEN
keys under the MS_DEF_PROV and MS_DEF_DSS_DH_PROV providers. This code
is also based on other code that I have that does it with the same
provider and key type - between which I cannot spot a difference in the
WinCrypt calls themselves other than that the old code does not try to
retrieve the size, it just assumes a certain size
(BLOBHEADER+RSAPUBHEADER+64bytes - safe for Win32/WinCrypt, but not
expandable or very portable).

Any advice, very much appreciated.

TIA,

Ben

[Doug Barlow]

TemporalBeing wrote:

>I am working to try to export a 3DES key to be used as a template, and
> am getting the NTE_BAD_KEY error during the export.

You're using the wrong blob type to export a 3DES key; that's probably
what's causing your error.

Try changing PRIVATEKEYBLOB to PLAINTEXTKEYBLOB.

PRIVATEKEYBLOB is specific to exporting the private portion of asymmetric
key pairs.

Doug Barlow
The Soft Pedal Shop
CSP Design & Development Consulting
http://www.SoftPedal.net

[TemporalBeing]

> TemporalBeing wrote:
> > I am working to try to export a 3DES key to be used as a template, and
> > am getting the NTE_BAD_KEY error during the export.

Doug Barlow wrote:
> You're using the wrong blob type to export a 3DES key; that's probably
> what's causing your error.

Okay. That sounds reasonable. I changed it over to use the exchange key
for this part (which is sufficient for what I was doing at that point).
Oh well...

I have another issue with CryptExportKey, but it'll be best for another
thread. Thanks.

Ben