Dart Requires Chilkat v11.0.0+

RSA-OAEP with SHA256 hashing

See more RSA Examples

RSA encrypt a SHA256 hash with OAEP padding. 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 pubkey = CkPublicKey();

  final sbPem = CkStringBuilder();
  final bCrlf = true;
  sbPem.appendLine('-----BEGIN PUBLIC KEY-----', bCrlf);
  sbPem.appendLine('MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEA33TqqLR3eeUmDtHS89qF', bCrlf);
  sbPem.appendLine('3p4MP7Wfqt2Zjj3lZjLjjCGDvwr9cJNlNDiuKboODgUiT4ZdPWbOiMAfDcDzlOxA', bCrlf);
  sbPem.appendLine('04DDnEFGAf+kDQiNSe2ZtqC7bnIc8+KSG/qOGQIVaay4Ucr6ovDkykO5Hxn7OU7s', bCrlf);
  sbPem.appendLine('Jp9TP9H0JH8zMQA6YzijYH9LsupTerrY3U6zyihVEDXXOv08vBHk50BMFJbE9iwF', bCrlf);
  sbPem.appendLine('wnxCsU5+UZUZYw87Uu0n4LPFS9BT8tUIvAfnRXIEWCha3KbFWmdZQZlyrFw0buUE', bCrlf);
  sbPem.appendLine('f0YN3/Q0auBkdbDR/ES2PbgKTJdkjc/rEeM0TxvOUf7HuUNOhrtAVEN1D5uuxE1W', bCrlf);
  sbPem.appendLine('SwIDAQAB', bCrlf);
  sbPem.appendLine('-----END PUBLIC KEY-----', bCrlf);

  // Load the public key object from the PEM. 
  try {
    pubkey.loadFromString(sbPem.getAsString());
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  // Build a small string to encrypt
  final json = CkJsonObject();
  json.updateString('example', '123');
  json.updateString('hello', 'world');
  print(json.emit());

  // This is the JSON to be RSA encrypted:  {"example":"123","hello":"world"}

  // IMPORTANT: RSA encryption is only used to encrypt small amounts of data.
  // RSA is only able to encrypt data to a maximum amount of your key size (2048 bits = 256 bytes) 
  // minus padding / header data (11 bytes for PKCS#1 v1.5 padding, 42 bytes for OAEP).
  // As a result it is often not possible to encrypt files with RSA directly. 
  // RSA is also not meant for this purpose. 
  // 
  // If you want to encrypt more data, you can use something like:
  // 1) Generate a 256-bit random keystring K
  // 2) Encrypt your data with AES-CBC with K
  // 3) Encrypt K with RSA
  // 4) Send both to the other side 

  final rsa = CkRsa();
  rsa.pkcsPadding = false;
  rsa.oaepHash = 'SHA-256';
  rsa.usePublicKey(pubkey);
  rsa.encodingMode = 'base64';

  // Note: The OAEP padding uses random bytes in the padding, and therefore each time encryption happens,
  // even using the same data and key, the result will be different --  but still valid.  One should not expect
  // to get the same output.
  final bUsePrivateKey = false;
  final String encryptedStr;
  try {
    encryptedStr = rsa.encryptStringENC(json.emit(), bUsePrivateKey);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  print('Result: $encryptedStr');
}