(Node.js) Encrypt File in Chunks using AES CBC

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

Install Chilkat for Node.js and Electron using npm at Chilkat npm packages for Node.js Chilkat npm packages for Electron on Windows, Linux, MacOSX, and ARM

var os = require('os');
if (os.platform() == 'win32') {  
    if (os.arch() == 'ia32') {
        var chilkat = require('@chilkat/ck-node21-win-ia32');
    } else {
        var chilkat = require('@chilkat/ck-node21-win64'); 
    }
} else if (os.platform() == 'linux') {
    if (os.arch() == 'arm') {
        var chilkat = require('@chilkat/ck-node21-arm');
    } else if (os.arch() == 'x86') {
        var chilkat = require('@chilkat/ck-node21-linux32');
    } else {
        var chilkat = require('@chilkat/ck-node21-linux64');
    }
} else if (os.platform() == 'darwin') {
    if (os.arch() == 'arm64') {
        var chilkat = require('@chilkat/ck-node21-mac-m1');
    } else {
        var chilkat = require('@chilkat/ck-node21-macosx');
    }
}

function chilkatExample() {

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

    var crypt = new chilkat.Crypt2();

    crypt.CryptAlgorithm = "aes";
    crypt.CipherMode = "cbc";
    crypt.KeyLength = 128;

    crypt.SetEncodedKey("000102030405060708090A0B0C0D0E0F","hex");
    crypt.SetEncodedIV("000102030405060708090A0B0C0D0E0F","hex");

    var fileToEncrypt = "qa_data/hamlet.xml";
    var facIn = new chilkat.FileAccess();
    var success = facIn.OpenForRead(fileToEncrypt);
    if (success !== true) {
        console.log("Failed to open file that is to be encrytped.");
        return;
    }

    var outputEncryptedFile = "qa_output/hamlet.enc";
    var facOutEnc = new chilkat.FileAccess();
    success = facOutEnc.OpenForWrite(outputEncryptedFile);
    if (success !== true) {
        console.log("Failed to encrypted output file.");
        return;
    }

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

    crypt.FirstChunk = true;
    crypt.LastChunk = false;

    var bd = new chilkat.BinData();

    var 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:
    var 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:
    var bSame = facIn.FileContentsEqual(fileToEncrypt,decryptedFile);
    console.log("bSame = " + bSame);

}

chilkatExample();