React Native

Add a Detached Signature (Header Placement Control)

Demonstrates the Chilkat Mime.AddDetachedSignature2 method, which creates the same multipart/signed structure as AddDetachedSignature, with a second argument controlling whether the existing message header fields are transferred to the new outer entity.

Note: The file paths are relative to the application's current working directory. Absolute paths may also be used. Supply the paths appropriate to your own environment.

Background: Signing wraps the content in a new outer multipart/signed, which raises the question of where the message-level headers (Subject, From, To) should live. This variant lets you choose: transfer them up to the outer entity so the signed message looks like a normal email, or leave them on the inner part. Transferring is typical for email; the finer control matters when the signed entity is embedded in a larger structure.

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React Native

import { Cert, Mime } from '@chilkat/react-native'

function chilkatExample() {
  const mime = new Mime();
  try {
    mime.setBodyFromPlainText('This message will be signed.');
  } catch {
    console.log(mime.lastErrorText);
    return;
  }

  // Load the signing certificate (which must have access to its private key) from a PFX file.
  // The PFX password should come from a secure source rather than being hard-coded.
  const pfxPassword = 'myPfxPassword';
  const cert = new Cert();
  try {
    cert.loadPfxFile('qa_data/signer.pfx', pfxPassword);
  } catch {
    console.log(cert.lastErrorText);
    return;
  }

  // AddDetachedSignature2 is the same as AddDetachedSignature, but the 2nd argument controls whether
  // the existing message header fields are transferred to the new outer multipart/signed entity.
  const transferHeaderFields = true;
  try {
    mime.addDetachedSignature2(cert, transferHeaderFields);
  } catch {
    console.log(mime.lastErrorText);
    return;
  }

  try {
    mime.saveMime('qa_output/signed.eml');
  } catch {
    console.log(mime.lastErrorText);
    return;
  }

  console.log('Detached signature added (headers transferred).');
}