main.dart

import 'dart:convert';
import 'dart:math';
import 'dart:typed_data';

import 'package:asn1lib/asn1lib.dart';
import 'package:convert/convert.dart' as convert;
import 'package:ejenti_master_agent/myGenerator.dart';
import 'package:encrypt/encrypt.dart';
import 'package:pointycastle/export.dart';

Uint8List createUint8ListFromString(String s) {
  var ret = new Uint8List(s.length);
  for (var i = 0; i < s.length; i++) {
    ret[i] = s.codeUnitAt(i);
  }
  return ret;
}

Uint8List createUint8ListFromHexString(String hex) {
  var result = new Uint8List(hex.length ~/ 2);
  for (var i = 0; i < hex.length; i += 2) {
    var num = hex.substring(i, i + 2);
    var byte = int.parse(num, radix: 16);
    result[i ~/ 2] = byte;
  }
  return result;
}

Uint8List createUint8ListFromSequentialNumbers(int len) {
  var ret = new Uint8List(len);
  for (var i = 0; i < len; i++) {
    ret[i] = i;
  }
  return ret;
}

String formatBytesAsHexString(Uint8List bytes) {
  var result = new StringBuffer();
  for (var i = 0; i < bytes.lengthInBytes; i++) {
    var part = bytes[i];
    result.write('${part < 16 ? '0' : ''}${part.toRadixString(16)}');
  }
  return result.toString();
}

List<int> decodePEM(pem) {
  var startsWith = [
    "-----BEGIN PUBLIC KEY-----",
    "-----BEGIN PRIVATE KEY-----"
  ];
  var endsWith = ["-----END PUBLIC KEY-----", "-----END PRIVATE KEY-----"];

  for (var s in startsWith) {
    if (pem.startsWith(s)) pem = pem.substring(s.length);
  }

  for (var s in endsWith) {
    if (pem.endsWith(s)) pem = pem.substring(0, pem.length - s.length);
  }

  pem = pem.replaceAll('\n', '');
  pem = pem.replaceAll('\r', '');

  return base64.decode(pem);
}

List<int> decodeHex(String hex) {
  hex = hex
      .replaceAll(':', '')
      .replaceAll('\n', '')
      .replaceAll('\r', '')
      .replaceAll('\t', '');
  return convert.hex.decode(hex);
}

class RsaKeyHelper {
  AsymmetricKeyPair<RSAPublicKey, RSAPrivateKey> generateKeyPair() {
    var keyParams =
        new RSAKeyGeneratorParameters(BigInt.parse('65537'), 4096, 12);

    var secureRandom = new FortunaRandom();
    var random = new Random.secure();
    List<int> seeds = [];
    for (int i = 0; i < 32; i++) {
      seeds.add(random.nextInt(255));
    }
    secureRandom.seed(new KeyParameter(new Uint8List.fromList(seeds)));

    var rngParams = new ParametersWithRandom(keyParams, secureRandom);
    var k = new MyRSAKeyGenerator();
    k.init(rngParams);

    return k.generateKeyPair();
  }

  String encrypt(String plaintext, RSAPublicKey publicKey) {
    var cipher = new RSAEngine()
      ..init(true, new PublicKeyParameter<RSAPublicKey>(publicKey));
    var cipherText =
        cipher.process(new Uint8List.fromList(plaintext.codeUnits));

    return new String.fromCharCodes(cipherText);
  }

  String decrypt(String ciphertext, RSAPrivateKey privateKey) {
    var cipher = new RSAEngine()
      ..init(false, new PrivateKeyParameter<RSAPrivateKey>(privateKey));
    var decrypted =
        cipher.process(new Uint8List.fromList(ciphertext.codeUnits));

    return new String.fromCharCodes(decrypted);
  }

  parsePublicKeyFromPem(pemString) {
    List<int> publicKeyDER = decodePEM(pemString);
    var asn1Parser = new ASN1Parser(publicKeyDER);
    var topLevelSeq = asn1Parser.nextObject() as ASN1Sequence;
    var publicKeyBitString = topLevelSeq.elements[1];

    var publicKeyAsn = new ASN1Parser(publicKeyBitString.contentBytes());
    ASN1Sequence publicKeySeq = publicKeyAsn.nextObject();
    var modulus = publicKeySeq.elements[0] as ASN1Integer;
    var exponent = publicKeySeq.elements[1] as ASN1Integer;

    RSAPublicKey rsaPublicKey =
        RSAPublicKey(modulus.valueAsBigInteger, exponent.valueAsBigInteger);

    return rsaPublicKey;
  }

  parsePrivateKeyFromPem(pemString) {
    List<int> privateKeyDER = decodePEM(pemString);
    var asn1Parser = new ASN1Parser(privateKeyDER);
    var topLevelSeq = asn1Parser.nextObject() as ASN1Sequence;
    var version = topLevelSeq.elements[0];
    var algorithm = topLevelSeq.elements[1];
    var privateKey = topLevelSeq.elements[2];

    asn1Parser = new ASN1Parser(privateKey.contentBytes());
    var pkSeq = asn1Parser.nextObject() as ASN1Sequence;

    version = pkSeq.elements[0];
    var modulus = pkSeq.elements[1] as ASN1Integer;
    var publicExponent = pkSeq.elements[2] as ASN1Integer;
    var privateExponent = pkSeq.elements[3] as ASN1Integer;
    var p = pkSeq.elements[4] as ASN1Integer;
    var q = pkSeq.elements[5] as ASN1Integer;
    var exp1 = pkSeq.elements[6] as ASN1Integer;
    var exp2 = pkSeq.elements[7] as ASN1Integer;
    var co = pkSeq.elements[8] as ASN1Integer;

    RSAPrivateKey rsaPrivateKey = RSAPrivateKey(
        modulus.valueAsBigInteger,
        privateExponent.valueAsBigInteger,
        p.valueAsBigInteger,
        q.valueAsBigInteger);

    return rsaPrivateKey;
  }

  encodePublicKeyToPem(RSAPublicKey publicKey) {
    var algorithmSeq = new ASN1Sequence();
    var algorithmAsn1Obj = new ASN1Object.fromBytes(Uint8List.fromList(
        [0x6, 0x9, 0x2a, 0x86, 0x48, 0x86, 0xf7, 0xd, 0x1, 0x1, 0x1]));
    var paramsAsn1Obj =
        new ASN1Object.fromBytes(Uint8List.fromList([0x5, 0x0]));
    algorithmSeq.add(algorithmAsn1Obj);
    algorithmSeq.add(paramsAsn1Obj);

    var publicKeySeq = new ASN1Sequence();
    publicKeySeq.add(ASN1Integer(publicKey.modulus));
    publicKeySeq.add(ASN1Integer(publicKey.exponent));
    var publicKeySeqBitString =
        new ASN1BitString(Uint8List.fromList(publicKeySeq.encodedBytes));

    var topLevelSeq = new ASN1Sequence();
    topLevelSeq.add(algorithmSeq);
    topLevelSeq.add(publicKeySeqBitString);
    var dataBase64 = base64.encode(topLevelSeq.encodedBytes);

    return """-----BEGIN PUBLIC KEY-----\r\n$dataBase64\r\n-----END PUBLIC KEY-----""";
  }

  encodePrivateKeyToPem(RSAPrivateKey privateKey) {
    var version = ASN1Integer(BigInt.from(0));

    var algorithmSeq = new ASN1Sequence();
    var algorithmAsn1Obj = new ASN1Object.fromBytes(Uint8List.fromList(
        [0x6, 0x9, 0x2a, 0x86, 0x48, 0x86, 0xf7, 0xd, 0x1, 0x1, 0x1]));
    var paramsAsn1Obj =
        new ASN1Object.fromBytes(Uint8List.fromList([0x5, 0x0]));
    algorithmSeq.add(algorithmAsn1Obj);
    algorithmSeq.add(paramsAsn1Obj);

    var privateKeySeq = new ASN1Sequence();
    var modulus = ASN1Integer(privateKey.n);
    var publicExponent = ASN1Integer(BigInt.parse('65537'));
    var privateExponent = ASN1Integer(privateKey.d);
    var p = ASN1Integer(privateKey.p);
    var q = ASN1Integer(privateKey.q);
    var dP = privateKey.d % (privateKey.p - BigInt.from(1));
    var exp1 = ASN1Integer(dP);
    var dQ = privateKey.d % (privateKey.q - BigInt.from(1));
    var exp2 = ASN1Integer(dQ);
    var iQ = privateKey.q.modInverse(privateKey.p);
    var co = ASN1Integer(iQ);

    privateKeySeq.add(version);
    privateKeySeq.add(modulus);
    privateKeySeq.add(publicExponent);
    privateKeySeq.add(privateExponent);
    privateKeySeq.add(p);
    privateKeySeq.add(q);
    privateKeySeq.add(exp1);
    privateKeySeq.add(exp2);
    privateKeySeq.add(co);
    var publicKeySeqOctetString =
        new ASN1OctetString(Uint8List.fromList(privateKeySeq.encodedBytes));

    var topLevelSeq = new ASN1Sequence();
    topLevelSeq.add(version);
    topLevelSeq.add(algorithmSeq);
    topLevelSeq.add(publicKeySeqOctetString);
    var dataBase64 = base64.encode(topLevelSeq.encodedBytes);

    return """-----BEGIN PRIVATE KEY-----\r\n$dataBase64\r\n-----END PRIVATE KEY-----""";
  }
}

main() {
//  var now = new DateTime.now();
//  var formatter = new DateFormat('dd-MM-yyyy: H:m');
//  String formatted = formatter.format(now);
//
//  print(now);
//
//  var rsaHelper = new RsaKeyHelper();
//  var keyPair = rsaHelper.generateKeyPair();
//  var encodedPrivateKey = rsaHelper.encodePrivateKeyToPem(keyPair.privateKey);
//  print(encodedPrivateKey);
//
//  var encodedPublicKey = rsaHelper.encodePublicKeyToPem(keyPair.publicKey);
//  print(encodedPublicKey);
//
//  var encodedMessage = rsaHelper.encrypt("Hello World", keyPair.publicKey);
//
//  var base64Message = base64.encode(utf8.encode(encodedMessage));
//
//  print('-----------Start Encrypting text--------------');
//  print(base64Message);
//  print('-----------End Encrypting text--------------');
//
//  var decodedMessage = base64.decode(base64Message);
//  var decoded =
//      rsaHelper.decrypt(utf8.decode(decodedMessage), keyPair.privateKey);
//  print('-----------Start Decrypting text--------------');
//  print(decoded);
//  print('-----------End Decrypting text--------------');

  /// Focus on this
  final key = 'my32lengthsupersecretnooneknows1';
  final encrypter = new Encrypter(new AES(key));
  var message = '1234567878';
  var encodedMessage = base64.encode(utf8.encode(message));
  final encryptedMessage = encrypter.encrypt(encodedMessage);
  print(encodedMessage);
  print(encryptedMessage);

  final decryptedMessage = encrypter.decrypt(encryptedMessage);
  print(decryptedMessage);
}