Dart Requires Chilkat v11.0.0+

Verfies an RSA Signature

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Verifies an RSA signature against the original data. Dart

import 'package:chilkat/chilkat.dart';

void main() {
  // The following data was signed by the following example:
  // RSA Sign using a Private Key on a USB Token or Smartcard
  final bd = CkBinData();
  for (var i = 0; i <= 100; i++) {
    bd.appendEncoded('000102030405060708090A0B0C0D0E0F', 'hex');
  }

  // Load the signature
  final bdSig = CkBinData();
  try {
    bdSig.loadFile('rsaSignatures/test1.sig');
  } on ChilkatException {
    print('Failed to load the RSA signature');
    return;
  }

  // Get the public key to be used for signature verification.
  final pubKey = CkPublicKey();
  try {
    pubKey.loadFromFile('rsaKeys/chilkat-rsa-2048.pem');
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  final rsa = CkRsa();
  try {
    rsa.usePublicKey(pubKey);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  // Verify the hash of the data against the signature.
  // We pass in the original data.  Internally, the hash is generated
  // and used to validate the signature.
  // Validating the RSA signature means two things:  
  // (1) the original data is exactly what was signed, and 
  // (2) it was signed by the owner of the RSA private key.

  try {
    rsa.verifyBd(bd, 'sha256', bdSig);
    print('Signature valid.');
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    print('Signature invalid.');
  }
}