(PHP ActiveX) Encrypt File in Chunks using AES CBC

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

Chilkat ActiveX Downloads ActiveX for 32-bit and 64-bit Windows Note: The php_com_dotnet.dll may need to be enabled inside of php.ini.

<?php

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

// For versions of Chilkat < 10.0.0, use new COM('Chilkat_9_5_0.Chilkat.Crypt2')
$crypt = new COM("Chilkat.Crypt2");

$crypt->CryptAlgorithm = 'aes';
$crypt->CipherMode = 'cbc';
$crypt->KeyLength = 128;

$crypt->SetEncodedKey('000102030405060708090A0B0C0D0E0F','hex');
$crypt->SetEncodedIV('000102030405060708090A0B0C0D0E0F','hex');

$fileToEncrypt = 'qa_data/hamlet.xml';
// For versions of Chilkat < 10.0.0, use new COM('Chilkat_9_5_0.Chilkat.FileAccess')
$facIn = new COM("Chilkat.FileAccess");
$success = $facIn->OpenForRead($fileToEncrypt);
if ($success != 1) {
    print 'Failed to open file that is to be encrytped.' . "\n";
    exit;
}

$outputEncryptedFile = 'qa_output/hamlet.enc';
// For versions of Chilkat < 10.0.0, use new COM('Chilkat_9_5_0.Chilkat.FileAccess')
$facOutEnc = new COM("Chilkat.FileAccess");
$success = $facOutEnc->OpenForWrite($outputEncryptedFile);
if ($success != 1) {
    print 'Failed to encrypted output file.' . "\n";
    exit;
}

// Let's encrypt in 10000 byte chunks.
$chunkSize = 10000;
$numChunks = $facIn->GetNumBlocks($chunkSize);

$crypt->FirstChunk = 1;
$crypt->LastChunk = 0;

// For versions of Chilkat < 10.0.0, use new COM('Chilkat_9_5_0.Chilkat.BinData')
$bd = new COM("Chilkat.BinData");

$i = 0;
while ($i < $numChunks) {
    $i = $i + 1;
    if ($i == $numChunks) {
        $crypt->LastChunk = 1;
    }

    // Read the next chunk from the file.
    // The last chunk will be whatever amount remains in the file..
    $bd->Clear();
    $facIn->FileReadBd($chunkSize,$bd);

    // Encrypt.
    $crypt->EncryptBd($bd);

    // Write the encrypted chunk to the output file.
    $facOutEnc->FileWriteBd($bd,0,0);

    $crypt->FirstChunk = 0;
}

// Make sure both FirstChunk and LastChunk are restored to 1 after
// encrypting or decrypting in chunks.  Otherwise subsequent encryptions/decryptions
// will produce unexpected results.
$crypt->FirstChunk = 1;
$crypt->LastChunk = 1;

$facIn->FileClose();
$facOutEnc->FileClose();

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

// Compare the contents of the decrypted file with the original file:
$bSame = $facIn->FileContentsEqual($fileToEncrypt,$decryptedFile);
print 'bSame = ' . $bSame . "\n";

?>