(Unicode C) Apple Keychain - Create RSA Signature

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Using an RSA private key stored in the Apple Keychain, create a signature by signing the SHA-256 hash of the provided string, then return the signature encoded in Base64 format.

Note: This example requires Chilkat v10.0.0 or greater.

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#include <C_CkCertW.h>
#include <C_CkRsaW.h>

void ChilkatSample(void)
    {
    HCkCertW cert;
    BOOL success;
    HCkRsaW rsa;
    const wchar_t *sigBase64;

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

    cert = CkCertW_Create();

    // On MacOS and iOS, the LoadByCommonName function will search the Apple Keychain for the matching certificate.

    // A digital certificate's Common Name (CN) is a field in the certificate that specifies the name of the entity the 
    // certificate is issued to. It is often used to identify the domain name, hostname, or organization the certificate represents. 

    // For example:
    // - In an SSL/TLS certificate for a website, the CN typically contains the domain name (e.g., "www.example.com").
    // - For certificates representing individuals or organizations, the CN might include the person's name or the organization's name.

    // The CN is part of the certificate's Subject field and is crucial for verifying that the certificate corresponds 
    // to the intended entity, especially in SSL/TLS communications.

    success = CkCertW_LoadByCommonName(cert,L"Example, Inc.");
    if (success == FALSE) {
        wprintf(L"%s\n",CkCertW_lastErrorText(cert));
        CkCertW_Dispose(cert);
        return;
    }

    rsa = CkRsaW_Create();
    success = CkRsaW_SetX509Cert(rsa,cert,TRUE);
    if (success == FALSE) {
        wprintf(L"%s\n",CkRsaW_lastErrorText(rsa));
        CkCertW_Dispose(cert);
        CkRsaW_Dispose(rsa);
        return;
    }

    // Generate an RSA signature by signing the SHA-256 hash of the provided string, 
    // then return the signature encoded in Base64 format.
    CkRsaW_putEncodingMode(rsa,L"base64");
    sigBase64 = CkRsaW_signStringENC(rsa,L"to be signed",L"sha256");
    if (CkRsaW_getLastMethodSuccess(rsa) == FALSE) {
        wprintf(L"%s\n",CkRsaW_lastErrorText(rsa));
        CkCertW_Dispose(cert);
        CkRsaW_Dispose(rsa);
        return;
    }

    wprintf(L"RSA Signature:\n");
    wprintf(L"%s\n",sigBase64);


    CkCertW_Dispose(cert);
    CkRsaW_Dispose(rsa);

    }