PHP

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. Chilkat2 PHP

<?php

use Chilkat2\BinData;
use Chilkat2\Crypt2;
use Chilkat2\FileAccess;

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

$crypt = new Crypt2();

$crypt->CryptAlgorithm = 'aes';
$crypt->CipherMode = 'cbc';
$crypt->KeyLength = 256;

$crypt->SetEncodedKey('000102030405060708090A0B0C0D0E0F000102030405060708090A0B0C0D0E0F', 'hex');
$crypt->SetEncodedIV('000102030405060708090A0B0C0D0E0F', 'hex');

$fileToEncrypt = 'qa_data/hamlet.xml';
$facIn = new FileAccess();
try {
    $facIn->OpenForRead($fileToEncrypt);
} catch (\Chilkat2\Exception $e) {
    echo "Failed to open file that is to be encrytped.\n";
    exit;
}

$outputEncryptedFile = 'c:/temp/qa_output/hamlet.enc';
$facOutEnc = new FileAccess();
try {
    $facOutEnc->OpenForWrite($outputEncryptedFile);
} catch (\Chilkat2\Exception $e) {
    echo "Failed to encrypted output file.\n";
    exit;
}

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

$crypt->FirstChunk = true;
$crypt->LastChunk = false;

$bd = new BinData();

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

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

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

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