(C) RSA Sign Binary Data and Verify (Recover the Original Data)

Demonstrates how to RSA sign binary data and then verify/recover the original data.

Note: This example uses methods introduced in Chilkat v9.5.0.77.

Note: This example requires Chilkat v11.0.0 or greater.

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#include <C_CkPrivateKey.h>
#include <C_CkRsa.h>
#include <C_CkBinData.h>
#include <C_CkPublicKey.h>

void ChilkatSample(void)
    {
    BOOL success;
    HCkPrivateKey privKey;
    HCkRsa rsa;
    const char *originalData;
    HCkBinData bd;
    HCkPublicKey pubKey;
    HCkRsa rsa2;
    BOOL bVerified;

    success = FALSE;

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

    // Load an RSA private key for signing.
    privKey = CkPrivateKey_Create();
    success = CkPrivateKey_LoadEncryptedPemFile(privKey,"qa_data/pem/rsa_passwd.pem","passwd");
    if (success == FALSE) {
        printf("%s\n",CkPrivateKey_lastErrorText(privKey));
        CkPrivateKey_Dispose(privKey);
        return;
    }

    rsa = CkRsa_Create();
    CkRsa_UsePrivateKey(rsa,privKey);

    // We have some binary data (in hex) to sign
    originalData = "0102030405060708090A";
    bd = CkBinData_Create();
    CkBinData_AppendEncoded(bd,originalData,"hex");

    // If successful, the contents of bd are replaced with the RSA signature.
    success = CkRsa_SignRawBd(rsa,bd);
    if (success == FALSE) {
        printf("%s\n",CkRsa_lastErrorText(rsa));
        CkPrivateKey_Dispose(privKey);
        CkRsa_Dispose(rsa);
        CkBinData_Dispose(bd);
        return;
    }

    // Show the RSA signature in base64
    printf("%s\n",CkBinData_getEncoded(bd,"base64"));

    // ------------------------------------------
    // Get the public key from the private key
    pubKey = CkPublicKey_Create();
    CkPrivateKey_ToPublicKey(privKey,pubKey);

    // Verify the signature and extract the original data.
    rsa2 = CkRsa_Create();
    CkRsa_UsePublicKey(rsa2,pubKey);

    bVerified = CkRsa_VerifyRawBd(rsa2,bd);
    printf("signature verified: %d\n",bVerified);

    // Show the original data:
    printf("original data: %s\n",CkBinData_getEncoded(bd,"hex"));


    CkPrivateKey_Dispose(privKey);
    CkRsa_Dispose(rsa);
    CkBinData_Dispose(bd);
    CkPublicKey_Dispose(pubKey);
    CkRsa_Dispose(rsa2);

    }