C++

RSA Encrypt String to Encoded Result and Reverse

See more RSA Examples

Demonstrates how to RSA encrypt a string to a base64 encoded result, and the reverse. C++

#include <CkGlobal.h>
#include <CkPublicKey.h>
#include <CkRsa.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.

    CkGlobal glob;
    glob.put_DefaultUtf8(true);

    //  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

    //  Encrypt the utf-8 byte representation of the string.
    rsa.put_Charset("utf-8");
    rsa.put_EncodingMode("base64");

    //  Be Careful when Using non-us-ascii String Literals in Source Code
    const char *encryptedB64 = rsa.encryptStringENC("Élève français dîne à côté d’un café où l’on sert déjà du gâteau au chocolat et des éclairs délicieux",false);

    //  ------------------------------------------------------------------------------------------------------------------------
    //  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);

    //  Indicate that after decrypting the resultant decrypted bytes contains the utf-8 byte representation of the text.
    rsa.put_Charset("utf-8");
    rsa.put_EncodingMode("base64");
    const char *originalText = rsa.decryptStringENC(encryptedB64,true);
    if (success == false) {
        std::cout << rsa.lastErrorText() << "\r\n";
        return;
    }

    std::cout << "Original text = " << originalText << "\r\n";
    std::cout << "Success." << "\r\n";
    }