JavaScript

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. JavaScript

var success = false;

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

var crypt = new CkCrypt2();

crypt.CryptAlgorithm = "aes";
crypt.CipherMode = "cbc";
crypt.KeyLength = 256;

crypt.SetEncodedKey("000102030405060708090A0B0C0D0E0F000102030405060708090A0B0C0D0E0F","hex");
crypt.SetEncodedIV("000102030405060708090A0B0C0D0E0F","hex");

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

var outputEncryptedFile = "c:/temp/qa_output/hamlet.enc";
var facOutEnc = new CkFileAccess();
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 CkBinData();

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);