Unicode C

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

See more RSA Examples

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.

Unicode C

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

void ChilkatSample(void)
    {
    BOOL success;
    HCkPrivateKeyW privKey;
    HCkRsaW rsa;
    const wchar_t *originalData;
    HCkBinDataW bd;
    HCkPublicKeyW pubKey;
    HCkRsaW 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 = CkPrivateKeyW_Create();
    success = CkPrivateKeyW_LoadEncryptedPemFile(privKey,L"qa_data/pem/rsa_passwd.pem",L"passwd");
    if (success == FALSE) {
        wprintf(L"%s\n",CkPrivateKeyW_lastErrorText(privKey));
        CkPrivateKeyW_Dispose(privKey);
        return;
    }

    rsa = CkRsaW_Create();
    CkRsaW_UsePrivateKey(rsa,privKey);

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

    // If successful, the contents of bd are replaced with the RSA signature.
    success = CkRsaW_SignRawBd(rsa,bd);
    if (success == FALSE) {
        wprintf(L"%s\n",CkRsaW_lastErrorText(rsa));
        CkPrivateKeyW_Dispose(privKey);
        CkRsaW_Dispose(rsa);
        CkBinDataW_Dispose(bd);
        return;
    }

    // Show the RSA signature in base64
    wprintf(L"%s\n",CkBinDataW_getEncoded(bd,L"base64"));

    // ------------------------------------------
    // Get the public key from the private key
    pubKey = CkPublicKeyW_Create();
    CkPrivateKeyW_ToPublicKey(privKey,pubKey);

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

    bVerified = CkRsaW_VerifyRawBd(rsa2,bd);
    wprintf(L"signature verified: %d\n",bVerified);

    // Show the original data:
    wprintf(L"original data: %s\n",CkBinDataW_getEncoded(bd,L"hex"));


    CkPrivateKeyW_Dispose(privKey);
    CkRsaW_Dispose(rsa);
    CkBinDataW_Dispose(bd);
    CkPublicKeyW_Dispose(pubKey);
    CkRsaW_Dispose(rsa2);

    }