(C) RSA Encrypt String to Encoded Result and Reverse

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

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#include <C_CkGlobal.h>
#include <C_CkPublicKey.h>
#include <C_CkRsa.h>
#include <C_CkPrivateKey.h>

void ChilkatSample(void)
    {
    HCkGlobal glob;
    HCkPublicKey pubKey;
    BOOL success;
    HCkRsa rsa;
    const char *encryptedB64;
    HCkPrivateKey privKey;
    const char *password;
    const char *originalText;

    // 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.

    glob = CkGlobal_Create();
    CkGlobal_putDefaultUtf8(glob,TRUE);

    // Load our 2048-bit RSA public key.
    pubKey = CkPublicKey_Create();
    // In all Chilkat methods expecting a path, you pass either absolute or relative paths.
    success = CkPublicKey_LoadFromFile(pubKey,"rsaKeys/myTestRsaPublic.pem");
    if (success == FALSE) {
        printf("%s\n",CkPublicKey_lastErrorText(pubKey));
        CkGlobal_Dispose(glob);
        CkPublicKey_Dispose(pubKey);
        return;
    }

    rsa = CkRsa_Create();

    // Tell RSA to use the public key.
    CkRsa_ImportPublicKeyObj(rsa,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.
    CkRsa_putCharset(rsa,"utf-8");
    CkRsa_putEncodingMode(rsa,"base64");

    // Be Careful when Using non-us-ascii String Literals in Source Code
    encryptedB64 = CkRsa_encryptStringENC(rsa,"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.
    privKey = CkPrivateKey_Create();
    password = "secret";
    success = CkPrivateKey_LoadAnyFormatFile(privKey,"rsaKeys/myTestRsaPrivate.pem",password);
    if (success == FALSE) {
        printf("%s\n",CkPrivateKey_lastErrorText(privKey));
        CkGlobal_Dispose(glob);
        CkPublicKey_Dispose(pubKey);
        CkRsa_Dispose(rsa);
        CkPrivateKey_Dispose(privKey);
        return;
    }

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

    // Indicate that after decrypting the resultant decrypted bytes contains the utf-8 byte representation of the text.
    CkRsa_putCharset(rsa,"utf-8");
    CkRsa_putEncodingMode(rsa,"base64");
    originalText = CkRsa_decryptStringENC(rsa,encryptedB64,TRUE);
    if (success == FALSE) {
        printf("%s\n",CkRsa_lastErrorText(rsa));
        CkGlobal_Dispose(glob);
        CkPublicKey_Dispose(pubKey);
        CkRsa_Dispose(rsa);
        CkPrivateKey_Dispose(privKey);
        return;
    }

    printf("Original text = %s\n",originalText);
    printf("Success.\n");


    CkGlobal_Dispose(glob);
    CkPublicKey_Dispose(pubKey);
    CkRsa_Dispose(rsa);
    CkPrivateKey_Dispose(privKey);

    }