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DataFlex Examples

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(DataFlex) Encrypt File in Chunks using AES CBC

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

Important This example requires Chilkat v9.5.0.68 or later.

Chilkat ActiveX Downloads

ActiveX for 32-bit and 64-bit Windows

Use ChilkatAx-9.5.0-win32.pkg

Procedure Test
    Handle hoCrypt
    String sFileToEncrypt
    Handle hoFacIn
    Boolean iSuccess
    String sOutputEncryptedFile
    Handle hoFacOutEnc
    Integer iChunkSize
    Integer iNumChunks
    Variant vBd
    Handle hoBd
    Integer i
    String sDecryptedFile
    Boolean iBSame

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

    Get Create (RefClass(cComChilkatCrypt2)) To hoCrypt
    If (Not(IsComObjectCreated(hoCrypt))) Begin
        Send CreateComObject of hoCrypt
    End

    Set ComCryptAlgorithm Of hoCrypt To "aes"
    Set ComCipherMode Of hoCrypt To "cbc"
    Set ComKeyLength Of hoCrypt To 128

    Send ComSetEncodedKey To hoCrypt "000102030405060708090A0B0C0D0E0F" "hex"
    Send ComSetEncodedIV To hoCrypt "000102030405060708090A0B0C0D0E0F" "hex"

    Move "qa_data/hamlet.xml" To sFileToEncrypt
    Get Create (RefClass(cComCkFileAccess)) To hoFacIn
    If (Not(IsComObjectCreated(hoFacIn))) Begin
        Send CreateComObject of hoFacIn
    End
    Get ComOpenForRead Of hoFacIn sFileToEncrypt To iSuccess
    If (iSuccess <> True) Begin
        Showln "Failed to open file that is to be encrytped."
        Procedure_Return
    End

    Move "qa_output/hamlet.enc" To sOutputEncryptedFile
    Get Create (RefClass(cComCkFileAccess)) To hoFacOutEnc
    If (Not(IsComObjectCreated(hoFacOutEnc))) Begin
        Send CreateComObject of hoFacOutEnc
    End
    Get ComOpenForWrite Of hoFacOutEnc sOutputEncryptedFile To iSuccess
    If (iSuccess <> True) Begin
        Showln "Failed to encrypted output file."
        Procedure_Return
    End

    // Let's encrypt in 10000 byte chunks.
    Move 10000 To iChunkSize
    Get ComGetNumBlocks Of hoFacIn iChunkSize To iNumChunks

    Set ComFirstChunk Of hoCrypt To True
    Set ComLastChunk Of hoCrypt To False

    Get Create (RefClass(cComChilkatBinData)) To hoBd
    If (Not(IsComObjectCreated(hoBd))) Begin
        Send CreateComObject of hoBd
    End

    Move 0 To i
    While (i < iNumChunks)
        Move i + 1 To i
        If (i = iNumChunks) Begin
            Set ComLastChunk Of hoCrypt To True
        End

        // Read the next chunk from the file.
        // The last chunk will be whatever amount remains in the file..
        Get ComClear Of hoBd To iSuccess
        Get pvComObject of hoBd to vBd
        Get ComFileReadBd Of hoFacIn iChunkSize vBd To iSuccess

        // Encrypt.
        Get pvComObject of hoBd to vBd
        Get ComEncryptBd Of hoCrypt vBd To iSuccess

        // Write the encrypted chunk to the output file.
        Get pvComObject of hoBd to vBd
        Get ComFileWriteBd Of hoFacOutEnc vBd 0 0 To iSuccess

        Set ComFirstChunk Of hoCrypt To False
    Loop

    // Make sure both FirstChunk and LastChunk are restored to True after
    // encrypting or decrypting in chunks.  Otherwise subsequent encryptions/decryptions
    // will produce unexpected results.
    Set ComFirstChunk Of hoCrypt To True
    Set ComLastChunk Of hoCrypt To True

    Send ComFileClose To hoFacIn
    Send ComFileClose To hoFacOutEnc

    // Decrypt the encrypted output file in a single call using CBC mode:
    Move "qa_output/hamlet_dec.xml" To sDecryptedFile
    Get ComCkDecryptFile Of hoCrypt sOutputEncryptedFile sDecryptedFile To iSuccess
    // Assume success for the example..

    // Compare the contents of the decrypted file with the original file:
    Get ComFileContentsEqual Of hoFacIn sFileToEncrypt sDecryptedFile To iBSame
    Showln "bSame = " iBSame


End_Procedure

 

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