React Native

CMS Sign Hash

Demonstrates how to use the SignHashENC method to sign a pre-computed hash. This method creates a CMS signature (PKCS7 detached signature).

This example requires Chilkat v9.5.0.90 or later.

React Native

import { Cert, Crypt2 } from '@chilkat/react-native'

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

  const crypt = new Crypt2();

  // Create the hash to be signed...
  crypt.hashAlgorithm = 'sha256';
  crypt.encodingMode = 'base64';
  crypt.charset = 'utf-8';
  // Create the SHA256 hash of a string using the utf-8 byte representation.
  // Return the hash as base64.
  const base64Hash = crypt.hashStringENC('This is the string to be hashed');

  // Load a certificate for signing.
  const cert = new Cert();
  try {
    cert.loadPfxFile('qa_data/pfx/cert_test123.pfx', 'test123');
  } catch {
    console.log(cert.lastErrorText);
    return;
  }

  crypt.setSigningCert(cert);

  // Sign the hash to create a base64 CMS signature (which does not contain the original data).
  // We can get the signature in a single line of base64 by specifying "base64", or 
  // we can get multi-line base64 by specifying "base64_mime".
  crypt.encodingMode = 'base64_mime';
  let base64CmsSig: string;
  try {
    base64CmsSig = await crypt.signHashENCAsync(base64Hash, 'sha256', 'base64');
  } catch {
    console.log(crypt.lastErrorText);
    return;
  }

  // Note: In the above call to SignHashENC, the encoding of the returned CMS signature is specified by the EncodingMode property.
  // However, the encoding of the passed-in hash is indicated by the 3rd argument.

  console.log(`CMS Signature: ${base64CmsSig}`);
}