attempting to use Microsoft CNG to generate DSA keys in C

Question

I need to code some cryptographic logic in C (.NET / C# is not an option). I've gotten as far as BCryptSetProperty in generating a key pair. The API consistently fails with STATUS_NOT_SUPPORTED / 0xC00000BB. I've tried variations on the parameters. I have not been able to find a C example for using BCryptSetProperty with DSA to generate keys. Any assistance is appreciated.

    NTSTATUS nts,nts2;
    BCRYPT_ALG_HANDLE hAlg = NULL;
    BCRYPT_KEY_HANDLE hKey = NULL;

    DWORD   cbCipherText = 0,
            cbPlainText = 0,
            cbData = 0,
            cbKeyObject = 0,
            cbBlockLen = 0,
            cbBlob = 0;

    // Get access to the algorithm
    try {
        nts = BCryptOpenAlgorithmProvider(&hAlg,
            BCRYPT_DSA_ALGORITHM,               // The algorithm we will be using
            MS_PRIMITIVE_PROVIDER,              // The default; this parameter could be NULL
            0 // | BCRYPT_PROV_DISPATCH         // This flag may only be used in driver
        );
    }
    catch(...) {}

    if (STATUS_SUCCESS != nts)
    {
        cout << "BCryptOpenAlgorithmProvider failed with status 0X" << std::hex << nts << endl;
        return nts;
    }

#define KEYSIZE 3072

    // Make an empty holder for our key
    nts = BCryptGenerateKeyPair(hAlg,
        &hKey,          // Empty new key
        KEYSIZE,        // Key length - 3072 max length for BCRYPT_DSA_ALGORITHM
        0);             // No flags defined
    if (STATUS_SUCCESS != nts) { cout << "BCryptGenerateKeyPair failed with status 0X" << hex << nts << endl; goto cleanup1; }

    // Set parameters to be used in generating the key into our empty holder

    // Build a header for the key

#define CBSEEDLENGTH 43
#define CBGROUPSIZE 32
#define CBKEYLENGTH 384

    struct _DSA_PARAMETER_BLOB
    {
        BCRYPT_DSA_PARAMETER_HEADER_V2 H;
        UCHAR Seed[CBSEEDLENGTH];      // Big-endian.
        UCHAR q[CBGROUPSIZE];          // Big-endian.
        UCHAR Modulus[CBKEYLENGTH];    // Big-endian.
        UCHAR Generator[CBKEYLENGTH];  // Big-endian.
    } dpb;

    dpb.H.cbLength = sizeof(dpb);
    dpb.H.dwMagic = BCRYPT_DSA_PARAMETERS_MAGIC_V2;
    dpb.H.cbKeyLength = CBKEYLENGTH;                    // 3072 / 8
    dpb.H.hashAlgorithm = DSA_HASH_ALGORITHM_SHA512;    // only the left 256 bits are used
    dpb.H.standardVersion = DSA_FIPS186_3;
    dpb.H.cbSeedLength = CBSEEDLENGTH;                  // For L == 3072, len(q) = 256, cbSeedLength (measured in bytes) must be >= len(q), so >=32
    dpb.H.cbGroupSize = CBGROUPSIZE;                    // Because L > 1024 (L == 3072) (groupsize ::= len(q))
    dpb.H.Count[0] = dpb.H.Count[1] = dpb.H.Count[2] = 0;
    dpb.H.Count[3] = 64;                                // # of iterations stored big endian


    nts = BCryptSetProperty(hAlg,   // Note: all of these calls reference the top level object - the algorithm
        BCRYPT_DSA_PARAMETERS,      // Setting parameters for key generation
        (PUCHAR)&dpb,               // Parameters struct
        sizeof(dpb),
        0);                         // No flags defined
    if (STATUS_SUCCESS != nts) { cout << "BCryptSetProperty failed with status 0X" << hex << nts << endl; goto cleanup2; }

attempting to use Microsoft CNG to generate DSA keys in C

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