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(Unicode C) Encrypt File in Chunks using AES CBCDemonstrates how to use the FirstChunk/LastChunk properties to encrypt a file chunk-by-chunk.
#include <C_CkCrypt2W.h> #include <C_CkFileAccessW.h> #include <C_CkBinDataW.h> void ChilkatSample(void) { HCkCrypt2W crypt; const wchar_t *fileToEncrypt; HCkFileAccessW facIn; BOOL success; const wchar_t *outputEncryptedFile; HCkFileAccessW facOutEnc; int chunkSize; int numChunks; HCkBinDataW bd; int i; const wchar_t *decryptedFile; BOOL bSame; // This example assumes the Chilkat API to have been previously unlocked. // See Global Unlock Sample for sample code. crypt = CkCrypt2W_Create(); CkCrypt2W_putCryptAlgorithm(crypt,L"aes"); CkCrypt2W_putCipherMode(crypt,L"cbc"); CkCrypt2W_putKeyLength(crypt,128); CkCrypt2W_SetEncodedKey(crypt,L"000102030405060708090A0B0C0D0E0F",L"hex"); CkCrypt2W_SetEncodedIV(crypt,L"000102030405060708090A0B0C0D0E0F",L"hex"); fileToEncrypt = L"qa_data/hamlet.xml"; facIn = CkFileAccessW_Create(); success = CkFileAccessW_OpenForRead(facIn,fileToEncrypt); if (success != TRUE) { wprintf(L"Failed to open file that is to be encrytped.\n"); CkCrypt2W_Dispose(crypt); CkFileAccessW_Dispose(facIn); return; } outputEncryptedFile = L"qa_output/hamlet.enc"; facOutEnc = CkFileAccessW_Create(); success = CkFileAccessW_OpenForWrite(facOutEnc,outputEncryptedFile); if (success != TRUE) { wprintf(L"Failed to encrypted output file.\n"); CkCrypt2W_Dispose(crypt); CkFileAccessW_Dispose(facIn); CkFileAccessW_Dispose(facOutEnc); return; } // Let's encrypt in 10000 byte chunks. chunkSize = 10000; numChunks = CkFileAccessW_GetNumBlocks(facIn,chunkSize); CkCrypt2W_putFirstChunk(crypt,TRUE); CkCrypt2W_putLastChunk(crypt,FALSE); bd = CkBinDataW_Create(); i = 0; while (i < numChunks) { i = i + 1; if (i == numChunks) { CkCrypt2W_putLastChunk(crypt,TRUE); } // Read the next chunk from the file. // The last chunk will be whatever amount remains in the file.. CkBinDataW_Clear(bd); CkFileAccessW_FileReadBd(facIn,chunkSize,bd); // Encrypt. CkCrypt2W_EncryptBd(crypt,bd); // Write the encrypted chunk to the output file. CkFileAccessW_FileWriteBd(facOutEnc,bd,0,0); CkCrypt2W_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. CkCrypt2W_putFirstChunk(crypt,TRUE); CkCrypt2W_putLastChunk(crypt,TRUE); CkFileAccessW_FileClose(facIn); CkFileAccessW_FileClose(facOutEnc); // Decrypt the encrypted output file in a single call using CBC mode: decryptedFile = L"qa_output/hamlet_dec.xml"; success = CkCrypt2W_CkDecryptFile(crypt,outputEncryptedFile,decryptedFile); // Assume success for the example.. // Compare the contents of the decrypted file with the original file: bSame = CkFileAccessW_FileContentsEqual(facIn,fileToEncrypt,decryptedFile); wprintf(L"bSame = %d\n",bSame); CkCrypt2W_Dispose(crypt); CkFileAccessW_Dispose(facIn); CkFileAccessW_Dispose(facOutEnc); CkBinDataW_Dispose(bd); } |
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