C

Demonstrate RSA Encrypt/Decrypt using BinData

See more RSA Examples

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

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

void ChilkatSample(void)
    {
    BOOL success;
    HCkPublicKey pubKey;
    HCkRsa rsa;
    HCkBinData bd;
    int i;
    HCkPrivateKey privKey;
    const char *password;

    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.
    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));
        CkPublicKey_Dispose(pubKey);
        return;
    }

    rsa = CkRsa_Create();

    //  Tell RSA to use the public key.
    CkRsa_UsePublicKey(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

    //  Create some binary data to encrypt.
    bd = CkBinData_Create();
    i = 0;
    for (i = 0; i <= 49; i++) {
        CkBinData_AppendByte(bd,i);
    }

    //  Show the bytes to be encrypted in hex format:
    printf("To be encrypted: %s\n",CkBinData_getEncoded(bd,"hex"));

    //  To be encrypted: 000102030405060708090A0B0C0D0E0F101112131415161718191A1B1C1D1E1F202122232425262728292A2B2C2D2E2F3031

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

    //  Now it is encrypted.
    printf("Encrypted size = %d\n",CkBinData_getNumBytes(bd));
    printf("%s\n",CkBinData_getEncoded(bd,"hex"));

    //  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.
    privKey = CkPrivateKey_Create();
    password = "secret";
    success = CkPrivateKey_LoadAnyFormatFile(privKey,"rsaKeys/myTestRsaPrivate.pem",password);
    if (success == FALSE) {
        printf("%s\n",CkPrivateKey_lastErrorText(privKey));
        CkPublicKey_Dispose(pubKey);
        CkRsa_Dispose(rsa);
        CkBinData_Dispose(bd);
        CkPrivateKey_Dispose(privKey);
        return;
    }

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

    //  Decrypt
    success = CkRsa_DecryptBd(rsa,bd,TRUE);
    if (success == FALSE) {
        printf("%s\n",CkRsa_lastErrorText(rsa));
        CkPublicKey_Dispose(pubKey);
        CkRsa_Dispose(rsa);
        CkBinData_Dispose(bd);
        CkPrivateKey_Dispose(privKey);
        return;
    }

    //  Examine the contents of bd to see if it now contains the unencrypted original data.
    printf("Decrypted: %s\n",CkBinData_getEncoded(bd,"hex"));

    //  Decrypted: 000102030405060708090A0B0C0D0E0F101112131415161718191A1B1C1D1E1F202122232425262728292A2B2C2D2E2F3031


    CkPublicKey_Dispose(pubKey);
    CkRsa_Dispose(rsa);
    CkBinData_Dispose(bd);
    CkPrivateKey_Dispose(privKey);

    }