Unicode C++

Verify an RSA Signature Against the Signed String

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Demonstrates how to validate an RSA Signature against the string that was signed. Unicode C++

#include <CkStringBuilderW.h>
#include <CkPublicKeyW.h>
#include <CkRsaW.h>

void ChilkatSample(void)
    {
    bool success = false;

    //  Create the same string we previously signed in this example: 
    //  RSA Sign utf-8 Bytes of String to get Base64 RSA Signature

    CkStringBuilderW sb;
    bool crlfLineEnding = true;
    int i;
    for (i = 0; i <= 10; i++) {
        sb.AppendLine(L"This is a test.",crlfLineEnding);
    }

    const wchar_t *base64_rsa_sig = L"gWgpEXQqvXN6wh0MuFXPiw2xCb8cnmdizBT1TD1Tpm2GlJ8gnD59DGSj35GGXk1tM+mCOvMa2uW/9gmz8p6A90JLbn918i/2wKGvcde4wXnzPO7JADSNn2UwYzf3rp4/q/JrHv1GZETRJhABSFqTxOgdmdbEJQE/zijOSctCtQAM2CTb6t2BO8uHKSSUAwPH2cbeWxqsaVRLT4ruk5nZOxhoLgLMSjupiSzbE8zSTkkFOEHD+Mbb2xwg85AI0E4DsUnp+hLwwtS0blesgSyvtBY8oJODJeFcJsR7JDOTPdzHQHgJRl/2A4ij5xT91TpXy7ok43jhT6O9j7Q3qrafIQ==";

    //  Get the public key to be used for signature verification.
    CkPublicKeyW pubKey;
    success = pubKey.LoadFromFile(L"rsaKeys/chilkat-rsa-2048.pem");
    if (success == false) {
        wprintf(L"%s\n",pubKey.lastErrorText());
        return;
    }

    CkRsaW rsa;
    success = rsa.UsePublicKey(pubKey);
    if (success == false) {
        wprintf(L"%s\n",rsa.lastErrorText());
        return;
    }

    //  Verify the string against the signature.
    //  We signed the utf-8 byte representation of the string, so we must indicate
    //  to also validate against the utf-8 byte representation.
    rsa.put_Charset(L"utf-8");
    rsa.put_EncodingMode(L"base64");
    const wchar_t *signedString = sb.getAsString();
    success = rsa.VerifyStringENC(signedString,L"sha256",base64_rsa_sig);

    if (success == false) {
        wprintf(L"%s\n",rsa.lastErrorText());
        wprintf(L"Signature invalid.\n");
    }
    else {
        wprintf(L"Signature valid.\n");
    }
    }