(C) Create a Hash Signature for Value Added Tax Audit SOAP Message for Angola

Demonstrates how to create a hash signature that is required in Value Added Tax Audit Files in Angola, Africa.

It is the following two instructions that should be used to create a hash value to be put into a <hash></hash> field in SOAP XML file containing the tax data for the VAT authorities:

openssl dgst -shal -sign private.pem -outRegisto1.shal Registo1.txt

then

openssl enc -base64 - in Registo1.shal -out Registo1.b64 -A

Chilkat C/C++ Library Downloads
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#include <C_CkPrivateKey.h>
#include <C_CkRsa.h>

void ChilkatSample(void)
    {
    HCkPrivateKey pkey;
    BOOL success;
    HCkRsa rsa;
    const char *b64sig;

    // This example requires the Chilkat API to have been previously unlocked.
    // See Global Unlock Sample for sample code.

    pkey = CkPrivateKey_Create();

    // Load the private key from an PEM file.
    // Provide the password in the 2nd argument.
    // If no password is needed, just pass an empty string.
    success = CkPrivateKey_LoadAnyFormatFile(pkey,"qa_data/rsa/rsaPrivKey_secret.pem","secret");
    if (success != TRUE) {
        printf("%s\n",CkPrivateKey_lastErrorText(pkey));
        CkPrivateKey_Dispose(pkey);
        return;
    }

    // Assuming this is an RSA private key..
    rsa = CkRsa_Create();

    // Import the private key into the RSA object:
    success = CkRsa_ImportPrivateKeyObj(rsa,pkey);
    if (success != TRUE) {
        printf("%s\n",CkRsa_lastErrorText(rsa));
        CkPrivateKey_Dispose(pkey);
        CkRsa_Dispose(rsa);
        return;
    }

    // OpenSSL uses big-endian.
    CkRsa_putLittleEndian(rsa,FALSE);

    // SHA1 hash and sign, and return base64.
    CkRsa_putEncodingMode(rsa,"base64");
    b64sig = CkRsa_signStringENC(rsa,"2018-05-18,2018-05-18T11:22:19;FAC 001/18;53.00;","sha1");
    printf("%s\n",b64sig);

    // The signature is equal in size to your private key.  For example, if you have a 1024-bit RSA key,
    // then 1024 bits = 128 bytes.   When 128 bytes is base64 encoded, the result is a string approximately
    // 4/3rds the size of the original.  128 * 4 / 3 = (approximately) 172 bytes.

    // If your RSA key is 2048-bits, then your signature will be twice as long.


    CkPrivateKey_Dispose(pkey);
    CkRsa_Dispose(rsa);

    }