(PHP Extension) Encrypt File in Chunks using AES CBC

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

Chilkat PHP Downloads PHP Extension for Windows, Linux, MacOS, Alpine Linux, Solaris

<?php

include("chilkat_9_5_0.php");

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

$crypt = new CkCrypt2();

$crypt->put_CryptAlgorithm('aes');
$crypt->put_CipherMode('cbc');
$crypt->put_KeyLength(128);

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

$fileToEncrypt = 'qa_data/hamlet.xml';
$facIn = new CkFileAccess();
$success = $facIn->OpenForRead($fileToEncrypt);
if ($success != true) {
    print 'Failed to open file that is to be encrytped.' . "\n";
    exit;
}

$outputEncryptedFile = 'qa_output/hamlet.enc';
$facOutEnc = new CkFileAccess();
$success = $facOutEnc->OpenForWrite($outputEncryptedFile);
if ($success != true) {
    print 'Failed to encrypted output file.' . "\n";
    exit;
}

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

$crypt->put_FirstChunk(true);
$crypt->put_LastChunk(false);

$bd = new CkBinData();

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

    // 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->put_FirstChunk(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.
$crypt->put_FirstChunk(true);
$crypt->put_LastChunk(true);

$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";

?>