C++

Demonstrate RSA Encrypt/Decrypt using BinData

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Demonstrates how to RSA encrypt and decrypt data contained in a Chilkat BinData object. C++

#include <CkPublicKey.h>
#include <CkRsa.h>
#include <CkBinData.h>
#include <CkPrivateKey.h>

void ChilkatSample(void)
    {
    bool success = false;

    //  The RSA public key is used for encryption, and the private key for decryption.

    //  The public key's role is to make encryption accessible to anyone while ensuring that
    //  only the private key holder can decrypt the messages.
    //  The public key is designed to be widely distributed so anyone can use it to encrypt messages
    //  intended for the owner of the private key.

    //  Load our 2048-bit RSA public key.
    CkPublicKey pubKey;
    //  In all Chilkat methods expecting a path, you pass either absolute or relative paths.
    success = pubKey.LoadFromFile("rsaKeys/myTestRsaPublic.pem");
    if (success == false) {
        std::cout << pubKey.lastErrorText() << "\r\n";
        return;
    }

    CkRsa rsa;

    //  Tell RSA to use the public key.
    rsa.UsePublicKey(pubKey);

    //  RSA encryption is for small amounts of data, on the order of 200 bytes or less.
    //  The maximum number of bytes that can be RSA encrypted depends
    //  on the RSA key size and padding scheme (OAEP padding vs PKCS#1 v1.5 padding).
    //  For specific limits, see: RSA Encryption Maximum Number of Bytes

    //  Create some binary data to encrypt.
    CkBinData bd;
    int i = 0;
    for (i = 0; i <= 49; i++) {
        bd.AppendByte(i);
    }

    //  Show the bytes to be encrypted in hex format:
    std::cout << "To be encrypted: " << bd.getEncoded("hex") << "\r\n";

    //  To be encrypted: 000102030405060708090A0B0C0D0E0F101112131415161718191A1B1C1D1E1F202122232425262728292A2B2C2D2E2F3031

    //  RSA encrypt the contents of the bd, replacing the contents with the RSA encrypted data.
    rsa.EncryptBd(bd,false);

    //  Now it is encrypted.
    std::cout << "Encrypted size = " << bd.get_NumBytes() << "\r\n";
    std::cout << bd.getEncoded("hex") << "\r\n";

    //  Encrypted size = 256
    //  749ED9D0A8767C06C09AD9697F654F86B145F966722F9714902C4175BDBD02E68984ECF111D4D461
    //  EDB4A8E677D399D19CCA60F35C6DE9972F4262880FE9D77DB75915393E8E7DB80AAB5E383013FAEB
    //  60C77D1E6FECC9A7C8426976416C6218FE7DA998EE063CE709E79C240F8625F4A56A0A33AFD63F7A
    //  BA26F2A692B42E878C53B78602C725FE63FF961A46A2B9D436E5E3D9D64AE3F1D1F5AD5F5B47FCD69
    //  447306B77F2FD6D766CCAA1A110A3371586B43DF0D7FFE2220D1B305CF9371AC342F849FB0C90CD99E
    //  C176928D877FE1C0DE1A7CB6EB824FEC7E1DCF90EF2C6BA9F1DFD3EBFBE89C51AF074DC6AE02E544A78
    //  5018C36D3D48B2EF5202AF61AC

    //  ------------------------------------------------------------------------------------------------------------------------
    //  Let's decrypt, which requires the matching private key...

    //  Load the matching 2048-bit RSA private key.
    CkPrivateKey privKey;
    const char *password = "secret";
    success = privKey.LoadAnyFormatFile("rsaKeys/myTestRsaPrivate.pem",password);
    if (success == false) {
        std::cout << privKey.lastErrorText() << "\r\n";
        return;
    }

    //  Tell the RSA object to use the private key.
    rsa.UsePrivateKey(privKey);

    //  Decrypt
    success = rsa.DecryptBd(bd,true);
    if (success == false) {
        std::cout << rsa.lastErrorText() << "\r\n";
        return;
    }

    //  Examine the contents of bd to see if it now contains the unencrypted original data.
    std::cout << "Decrypted: " << bd.getEncoded("hex") << "\r\n";

    //  Decrypted: 000102030405060708090A0B0C0D0E0F101112131415161718191A1B1C1D1E1F202122232425262728292A2B2C2D2E2F3031
    }