(C) Verfies an RSA Signature

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Verifies an RSA signature against the original data.

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

void ChilkatSample(void)
    {
    HCkBinData bd;
    int i;
    HCkBinData bdSig;
    BOOL success;
    HCkPublicKey pubKey;
    HCkRsa rsa;

    // The following data was signed by the following example:
    // RSA Sign using a Private Key on a USB Token or Smartcard
    bd = CkBinData_Create();

    for (i = 0; i <= 100; i++) {
        CkBinData_AppendEncoded(bd,"000102030405060708090A0B0C0D0E0F","hex");
    }

    // Load the signature
    bdSig = CkBinData_Create();
    success = CkBinData_LoadFile(bdSig,"rsaSignatures/test1.sig");
    if (success == FALSE) {
        printf("Failed to load the RSA signature\n");
        CkBinData_Dispose(bd);
        CkBinData_Dispose(bdSig);
        return;
    }

    // Get the public key to be used for signature verification.
    pubKey = CkPublicKey_Create();
    success = CkPublicKey_LoadFromFile(pubKey,"rsaKeys/chilkat-rsa-2048.pem");
    if (success == FALSE) {
        printf("%s\n",CkPublicKey_lastErrorText(pubKey));
        CkBinData_Dispose(bd);
        CkBinData_Dispose(bdSig);
        CkPublicKey_Dispose(pubKey);
        return;
    }

    rsa = CkRsa_Create();
    CkRsa_ImportPublicKeyObj(rsa,pubKey);

    // Verify the hash of the data against the signature.
    // We pass in the original data.  Internally, the hash is generated
    // and used to validate the signature.
    // Validating the RSA signature means two things:  
    // (1) the original data is exactly what was signed, and 
    // (2) it was signed by the owner of the RSA private key.
    success = CkRsa_VerifyBd(rsa,bd,"sha256",bdSig);

    if (success == FALSE) {
        printf("%s\n",CkRsa_lastErrorText(rsa));
        printf("Signature invalid.\n");
    }
    else {
        printf("Signature valid.\n");
    }



    CkBinData_Dispose(bd);
    CkBinData_Dispose(bdSig);
    CkPublicKey_Dispose(pubKey);
    CkRsa_Dispose(rsa);

    }