C

AES Encrypt and Decrypt a File

_LANGUAGE_ demonstrates how to AES encrypt a file of any size, and then decrypt. C

#include <C_CkCrypt2.h>

void ChilkatSample(void)
    {
    BOOL success;
    HCkCrypt2 crypt;
    const char *ivHex;
    const char *keyHex;
    const char *inFile;
    const char *outFile;
    HCkCrypt2 decrypt;

    success = FALSE;

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

    crypt = CkCrypt2_Create();

    CkCrypt2_putCryptAlgorithm(crypt,"aes");

    //  CipherMode may be "ecb" or "cbc"
    CkCrypt2_putCipherMode(crypt,"cbc");

    //  KeyLength may be 128, 192, 256
    CkCrypt2_putKeyLength(crypt,256);

    //  The padding scheme determines the contents of the bytes
    //  that are added to pad the result to a multiple of the
    //  encryption algorithm's block size.  AES has a block
    //  size of 16 bytes, so encrypted output is always
    //  a multiple of 16.
    CkCrypt2_putPaddingScheme(crypt,0);

    //  An initialization vector is required if using CBC mode.
    //  ECB mode does not use an IV.
    //  The length of the IV is equal to the algorithm's block size.
    //  It is NOT equal to the length of the key.
    ivHex = "000102030405060708090A0B0C0D0E0F";
    CkCrypt2_SetEncodedIV(crypt,ivHex,"hex");

    //  The secret key must equal the size of the key.  For
    //  256-bit encryption, the binary secret key is 32 bytes.
    //  For 128-bit encryption, the binary secret key is 16 bytes.
    keyHex = "000102030405060708090A0B0C0D0E0F101112131415161718191A1B1C1D1E1F";
    CkCrypt2_SetEncodedKey(crypt,keyHex,"hex");

    //  Encrypt a file, producing the .aes as output.
    //  The input file is unchanged, the output .aes contains the encrypted
    //  contents of the input file.

    //  Note: The .aes output file has no file format.  It is simply a stream
    //  of bytes that resembles random binary data.
    inFile = "/Users/chilkat/testData/pdf/sample.pdf";
    outFile = "/Users/chilkat/testData/p7m/sample.pdf.aes";
    success = CkCrypt2_CkEncryptFile(crypt,inFile,outFile);
    if (success != TRUE) {
        printf("%s\n",CkCrypt2_lastErrorText(crypt));
        CkCrypt2_Dispose(crypt);
        return;
    }

    //  For demonstration purposes, a different instance of the object will be used
    //  for decryption.
    decrypt = CkCrypt2_Create();

    //  All settings must match to be able to decrypt:
    CkCrypt2_putCryptAlgorithm(decrypt,"aes");
    CkCrypt2_putCipherMode(decrypt,"cbc");
    CkCrypt2_putKeyLength(decrypt,256);
    CkCrypt2_putPaddingScheme(decrypt,0);
    CkCrypt2_SetEncodedIV(decrypt,ivHex,"hex");
    CkCrypt2_SetEncodedKey(decrypt,keyHex,"hex");

    //  Decrypt the .aes
    inFile = "/Users/chilkat/testData/p7m/sample.pdf.aes";
    outFile = "/Users/chilkat/testData/pdf/recovered.pdf";
    success = CkCrypt2_CkDecryptFile(decrypt,inFile,outFile);
    if (success == FALSE) {
        printf("%s\n",CkCrypt2_lastErrorText(decrypt));
        CkCrypt2_Dispose(crypt);
        CkCrypt2_Dispose(decrypt);
        return;
    }

    printf("Success!\n");


    CkCrypt2_Dispose(crypt);
    CkCrypt2_Dispose(decrypt);

    }