Unicode C

RSA Signature/Verify with .key and .cer

See more RSA Examples

Demonstrates how to use a .key file (private key) and digital certificate (.cer, public key) to create and verify an RSA signature. Unicode C

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

void ChilkatSample(void)
    {
    BOOL success;
    HCkPrivateKeyW privKey;
    HCkRsaW rsa;
    const wchar_t *strData;
    const wchar_t *hexSig;
    HCkCertW cert;
    HCkPublicKeyW pubKey;
    HCkRsaW rsa2;

    success = FALSE;

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

    privKey = CkPrivateKeyW_Create();

    // Load the private key from an RSA .key file:
    success = CkPrivateKeyW_LoadPemFile(privKey,L"privateKey.key");
    if (success == FALSE) {
        wprintf(L"%s\n",CkPrivateKeyW_lastErrorText(privKey));
        CkPrivateKeyW_Dispose(privKey);
        return;
    }

    rsa = CkRsaW_Create();

    // Import the private key into the RSA component:
    success = CkRsaW_UsePrivateKey(rsa,privKey);
    if (success == FALSE) {
        wprintf(L"%s\n",CkRsaW_lastErrorText(rsa));
        CkPrivateKeyW_Dispose(privKey);
        CkRsaW_Dispose(rsa);
        return;
    }

    // Create the signature as a hex string:
    CkRsaW_putEncodingMode(rsa,L"hex");

    strData = L"This is the string to be signed.";

    // Sign the string using the sha256 hash algorithm.
    // Other valid choices are "md2", "sha1", "sha384",
    // "sha512", and "md5".
    hexSig = CkRsaW_signStringENC(rsa,strData,L"sha256");

    wprintf(L"%s\n",hexSig);

    // Load a digital certificate from a .cer file:
    cert = CkCertW_Create();

    success = CkCertW_LoadFromFile(cert,L"myCert.cer");
    if (success == FALSE) {
        wprintf(L"%s\n",CkCertW_lastErrorText(cert));
        CkPrivateKeyW_Dispose(privKey);
        CkRsaW_Dispose(rsa);
        CkCertW_Dispose(cert);
        return;
    }

    pubKey = CkPublicKeyW_Create();
    CkCertW_GetPublicKey(cert,pubKey);

    // Now verify using a new instance of the RSA object:
    rsa2 = CkRsaW_Create();

    // Import the public key into the RSA object:
    success = CkRsaW_UsePublicKey(rsa2,pubKey);
    if (success == FALSE) {
        wprintf(L"%s\n",CkRsaW_lastErrorText(rsa2));
        CkPrivateKeyW_Dispose(privKey);
        CkRsaW_Dispose(rsa);
        CkCertW_Dispose(cert);
        CkPublicKeyW_Dispose(pubKey);
        CkRsaW_Dispose(rsa2);
        return;
    }

    // The signature is a hex string, so make sure the EncodingMode is correct:
    CkRsaW_putEncodingMode(rsa2,L"hex");

    // Verify the signature:
    success = CkRsaW_VerifyStringENC(rsa2,strData,L"sha256",hexSig);
    if (success == FALSE) {
        wprintf(L"%s\n",CkRsaW_lastErrorText(rsa2));
        CkPrivateKeyW_Dispose(privKey);
        CkRsaW_Dispose(rsa);
        CkCertW_Dispose(cert);
        CkPublicKeyW_Dispose(pubKey);
        CkRsaW_Dispose(rsa2);
        return;
    }

    wprintf(L"Success.\n");


    CkPrivateKeyW_Dispose(privKey);
    CkRsaW_Dispose(rsa);
    CkCertW_Dispose(cert);
    CkPublicKeyW_Dispose(pubKey);
    CkRsaW_Dispose(rsa2);

    }