C

Encrypt File in Chunks using AES CBC

See more Encryption Examples

Demonstrates how to use the FirstChunk/LastChunk properties to encrypt a file chunk-by-chunk. C

#include <C_CkCrypt2.h>
#include <C_CkFileAccess.h>
#include <C_CkBinData.h>

void ChilkatSample(void)
    {
    BOOL success;
    HCkCrypt2 crypt;
    const char *fileToEncrypt;
    HCkFileAccess facIn;
    const char *outputEncryptedFile;
    HCkFileAccess facOutEnc;
    int chunkSize;
    int numChunks;
    HCkBinData bd;
    int i;
    const char *decryptedFile;
    BOOL bSame;

    success = FALSE;

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

    crypt = CkCrypt2_Create();

    CkCrypt2_putCryptAlgorithm(crypt,"aes");
    CkCrypt2_putCipherMode(crypt,"cbc");
    CkCrypt2_putKeyLength(crypt,256);

    CkCrypt2_SetEncodedKey(crypt,"000102030405060708090A0B0C0D0E0F000102030405060708090A0B0C0D0E0F","hex");
    CkCrypt2_SetEncodedIV(crypt,"000102030405060708090A0B0C0D0E0F","hex");

    fileToEncrypt = "qa_data/hamlet.xml";
    facIn = CkFileAccess_Create();
    success = CkFileAccess_OpenForRead(facIn,fileToEncrypt);
    if (success != TRUE) {
        printf("Failed to open file that is to be encrytped.\n");
        CkCrypt2_Dispose(crypt);
        CkFileAccess_Dispose(facIn);
        return;
    }

    outputEncryptedFile = "c:/temp/qa_output/hamlet.enc";
    facOutEnc = CkFileAccess_Create();
    success = CkFileAccess_OpenForWrite(facOutEnc,outputEncryptedFile);
    if (success != TRUE) {
        printf("Failed to encrypted output file.\n");
        CkCrypt2_Dispose(crypt);
        CkFileAccess_Dispose(facIn);
        CkFileAccess_Dispose(facOutEnc);
        return;
    }

    // Let's encrypt in 10000 byte chunks.
    chunkSize = 10000;
    numChunks = CkFileAccess_GetNumBlocks(facIn,chunkSize);

    CkCrypt2_putFirstChunk(crypt,TRUE);
    CkCrypt2_putLastChunk(crypt,FALSE);

    bd = CkBinData_Create();

    i = 0;
    while (i < numChunks) {
        i = i + 1;
        if (i == numChunks) {
            CkCrypt2_putLastChunk(crypt,TRUE);
        }

        // Read the next chunk from the file.
        // The last chunk will be whatever amount remains in the file..
        CkBinData_Clear(bd);
        CkFileAccess_FileReadBd(facIn,chunkSize,bd);

        // Encrypt.
        CkCrypt2_EncryptBd(crypt,bd);

        // Write the encrypted chunk to the output file.
        CkFileAccess_FileWriteBd(facOutEnc,bd,0,0);

        CkCrypt2_putFirstChunk(crypt,FALSE);
    }

    // Make sure both FirstChunk and LastChunk are restored to TRUE after
    // encrypting or decrypting in chunks.  Otherwise subsequent encryptions/decryptions
    // will produce unexpected results.
    CkCrypt2_putFirstChunk(crypt,TRUE);
    CkCrypt2_putLastChunk(crypt,TRUE);

    CkFileAccess_FileClose(facIn);
    CkFileAccess_FileClose(facOutEnc);

    // Decrypt the encrypted output file in a single call using CBC mode:
    decryptedFile = "qa_output/hamlet_dec.xml";
    success = CkCrypt2_CkDecryptFile(crypt,outputEncryptedFile,decryptedFile);
    // Assume success for the example..

    // Compare the contents of the decrypted file with the original file:
    bSame = CkFileAccess_FileContentsEqual(facIn,fileToEncrypt,decryptedFile);
    printf("bSame = %d\n",bSame);


    CkCrypt2_Dispose(crypt);
    CkFileAccess_Dispose(facIn);
    CkFileAccess_Dispose(facOutEnc);
    CkBinData_Dispose(bd);

    }