(C) RSA Encrypt and Decrypt Strings

C sample code to RSA public-key encrypt and decrypt strings using public and private keys.

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#include <C_CkRsa.h>

void ChilkatSample(void)
    {
    HCkRsa rsa;
    BOOL success;
    const char *publicKey;
    const char *privateKey;
    const char *plainText;
    HCkRsa rsaEncryptor;
    BOOL usePrivateKey;
    const char *encryptedStr;
    HCkRsa rsaDecryptor;
    const char *decryptedStr;

    // This example assumes the Chilkat API to have been previously unlocked.
    // See Global Unlock Sample for sample code.

    rsa = CkRsa_Create();

    // This example also generates the public and private
    // keys to be used in the RSA encryption.
    // Normally, you would generate a key pair once,
    // and distribute the public key to your partner.
    // Anything encrypted with the public key can be
    // decrypted with the private key.  The reverse is 
    // also true: anything encrypted using the private
    // key can be decrypted using the public key.

    // Generate a 1024-bit key.  Chilkat RSA supports
    // key sizes ranging from 512 bits to 4096 bits.
    success = CkRsa_GenerateKey(rsa,1024);
    if (success != TRUE) {
        printf("%s\n",CkRsa_lastErrorText(rsa));
        CkRsa_Dispose(rsa);
        return;
    }

    // Keys are exported in XML format:
    publicKey = CkRsa_exportPublicKey(rsa);
    privateKey = CkRsa_exportPrivateKey(rsa);

    plainText = "Encrypting and decrypting should be easy!";

    // Start with a new RSA object to demonstrate that all we
    // need are the keys previously exported:
    rsaEncryptor = CkRsa_Create();

    // Encrypted output is always binary.  In this case, we want
    // to encode the encrypted bytes in a printable string.
    // Our choices are "hex", "base64", "url", "quoted-printable".
    CkRsa_putEncodingMode(rsaEncryptor,"hex");

    // We'll encrypt with the public key and decrypt with the private
    // key.  It's also possible to do the reverse.
    success = CkRsa_ImportPublicKey(rsaEncryptor,publicKey);

    usePrivateKey = FALSE;
    encryptedStr = CkRsa_encryptStringENC(rsaEncryptor,plainText,usePrivateKey);
    printf("%s\n",encryptedStr);

    // Now decrypt:
    rsaDecryptor = CkRsa_Create();

    CkRsa_putEncodingMode(rsaDecryptor,"hex");
    success = CkRsa_ImportPrivateKey(rsaDecryptor,privateKey);

    usePrivateKey = TRUE;
    decryptedStr = CkRsa_decryptStringENC(rsaDecryptor,encryptedStr,usePrivateKey);

    printf("%s\n",decryptedStr);


    CkRsa_Dispose(rsa);
    CkRsa_Dispose(rsaEncryptor);
    CkRsa_Dispose(rsaDecryptor);

    }