Dart

Encrypt a File to a PKCS7 (CMS) Message

Shows how to encrypt a file into a PKCS7 encrypted message using the recipient's certificate. Public-key encryption requires no private key. However, the recipient's private key is necessary for decryption. Dart

import 'package:chilkat/chilkat.dart';

void main() {
  // This example requires the Chilkat API to have been previously unlocked.
  // See Global Unlock Sample for sample code.

  final crypt = CkCrypt2();

  // Load the recipient's digital certificate. 
  // We don't need the private key for encryption.
  // Only the public key is needed (which is included in a certificate).
  final cert1 = CkCert();
  cert1.loadFromFile('qa_data/user1/cert_user1.pem');
  // Assume success for the example, but make sure your application checks for success/failure...
  crypt.setEncryptCert(cert1);

  // Indicate that we want PKI encryption (i.e. public-key infrastructure)
  // to produce a CMS message (Cryptographic Message Syntax/PKCS7),
  // that is be created with RSAES-OAEP padding, SHA256, and AES-256 for the
  // bulk encryption.
  crypt.cryptAlgorithm = 'pki';
  crypt.pkcs7CryptAlg = 'aes';
  crypt.keyLength = 256;
  crypt.oaepHash = 'sha256';
  crypt.oaepPadding = true;

  // Load the file to be encrypted...
  final fileData = CkBinData();
  fileData.loadFile('qa_data/jpg/penguins.jpg');
  // Your app should check for success/failure..

  // Encrypt the data.  The contents of the fileData object are replaced with the PKCS7 encrypted message.
  try {
    crypt.encryptBd(fileData);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  // Save the PKCS7 encrypted message to a file..
  fileData.writeFile('qa_output/pkcs7_encrypted.p7');

  print('OK.');
}