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@proteye
Created September 5, 2018 10:54
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How to AES-256 (CBC/CFB mode) encrypt and decrypt in Dart/Flutter with Pointy Castle
import 'dart:convert';
import 'dart:typed_data';
import "package:pointycastle/export.dart";
import "./convert_helper.dart";
// AES key size
const KEY_SIZE = 32; // 32 byte key for AES-256
const ITERATION_COUNT = 1000;
class AesHelper {
static const CBC_MODE = 'CBC';
static const CFB_MODE = 'CFB';
static Uint8List deriveKey(dynamic password,
{String salt = '',
int iterationCount = ITERATION_COUNT,
int derivedKeyLength = KEY_SIZE}) {
if (password == null || password.isEmpty) {
throw new ArgumentError('password must not be empty');
}
if (password is String) {
password = createUint8ListFromString(password);
}
Uint8List saltBytes = createUint8ListFromString(salt);
Pbkdf2Parameters params =
new Pbkdf2Parameters(saltBytes, iterationCount, derivedKeyLength);
KeyDerivator keyDerivator =
new PBKDF2KeyDerivator(new HMac(new SHA256Digest(), 64));
keyDerivator.init(params);
return keyDerivator.process(password);
}
static Uint8List pad(Uint8List src, int blockSize) {
var pad = new PKCS7Padding();
pad.init(null);
int padLength = blockSize - (src.length % blockSize);
var out = new Uint8List(src.length + padLength)..setAll(0, src);
pad.addPadding(out, src.length);
return out;
}
static Uint8List unpad(Uint8List src) {
var pad = new PKCS7Padding();
pad.init(null);
int padLength = pad.padCount(src);
int len = src.length - padLength;
return new Uint8List(len)..setRange(0, len, src);
}
static String encrypt(String password, String plaintext,
{String mode = CBC_MODE}) {
Uint8List derivedKey = deriveKey(password);
KeyParameter keyParam = new KeyParameter(derivedKey);
BlockCipher aes = new AESFastEngine();
var rnd = FortunaRandom();
rnd.seed(keyParam);
Uint8List iv = rnd.nextBytes(aes.blockSize);
BlockCipher cipher;
ParametersWithIV params = new ParametersWithIV(keyParam, iv);
switch (mode) {
case CBC_MODE:
cipher = new CBCBlockCipher(aes);
break;
case CFB_MODE:
cipher = new CFBBlockCipher(aes, aes.blockSize);
break;
default:
throw new ArgumentError('incorrect value of the "mode" parameter');
break;
}
cipher.init(true, params);
Uint8List textBytes = createUint8ListFromString(plaintext);
Uint8List paddedText = pad(textBytes, aes.blockSize);
Uint8List cipherBytes = _processBlocks(cipher, paddedText);
Uint8List cipherIvBytes = new Uint8List(cipherBytes.length + iv.length)
..setAll(0, iv)
..setAll(iv.length, cipherBytes);
return base64.encode(cipherIvBytes);
}
static String decrypt(String password, String ciphertext,
{String mode = CBC_MODE}) {
Uint8List derivedKey = deriveKey(password);
KeyParameter keyParam = new KeyParameter(derivedKey);
BlockCipher aes = new AESFastEngine();
Uint8List cipherIvBytes = base64.decode(ciphertext);
Uint8List iv = new Uint8List(aes.blockSize)
..setRange(0, aes.blockSize, cipherIvBytes);
BlockCipher cipher;
ParametersWithIV params = new ParametersWithIV(keyParam, iv);
switch (mode) {
case CBC_MODE:
cipher = new CBCBlockCipher(aes);
break;
case CFB_MODE:
cipher = new CFBBlockCipher(aes, aes.blockSize);
break;
default:
throw new ArgumentError('incorrect value of the "mode" parameter');
break;
}
cipher.init(false, params);
int cipherLen = cipherIvBytes.length - aes.blockSize;
Uint8List cipherBytes = new Uint8List(cipherLen)
..setRange(0, cipherLen, cipherIvBytes, aes.blockSize);
Uint8List paddedText = _processBlocks(cipher, cipherBytes);
Uint8List textBytes = unpad(paddedText);
return new String.fromCharCodes(textBytes);
}
static Uint8List _processBlocks(BlockCipher cipher, Uint8List inp) {
var out = new Uint8List(inp.lengthInBytes);
for (var offset = 0; offset < inp.lengthInBytes;) {
var len = cipher.processBlock(inp, offset, out, offset);
offset += len;
}
return out;
}
}
import "dart:typed_data";
import 'dart:convert';
import 'package:convert/convert.dart' as convert;
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(String pem) {
var startsWith = [
"-----BEGIN PUBLIC KEY-----",
"-----BEGIN PRIVATE KEY-----",
"-----BEGIN ENCRYPTED MESSAGE-----",
"-----BEGIN PGP PUBLIC KEY BLOCK-----\r\nVersion: React-Native-OpenPGP.js 0.1\r\nComment: http://openpgpjs.org\r\n\r\n",
"-----BEGIN PGP PRIVATE KEY BLOCK-----\r\nVersion: React-Native-OpenPGP.js 0.1\r\nComment: http://openpgpjs.org\r\n\r\n",
];
var endsWith = [
"-----END PUBLIC KEY-----",
"-----END PRIVATE KEY-----",
"-----END ENCRYPTED MESSAGE-----",
"-----END PGP PUBLIC KEY BLOCK-----",
"-----END PGP PRIVATE KEY BLOCK-----",
];
bool isOpenPgp = pem.indexOf('BEGIN PGP') != -1;
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);
}
}
if (isOpenPgp) {
var index = pem.indexOf('\r\n');
pem = pem.substring(0, index);
}
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);
}
@bishalstha
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Hi,
I wanted to use this for my own mobile project and It found that the ITERATION_COUNT is too large in the mobile operation and seems to block execution time(for like at least like1-2 sec) even when used with future async. So, I reduced it to 250 which didn't block the execution that long.
My question is, is it alright to reduce the ITERATION_COUNT?

@InGuuuW
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InGuuuW commented May 22, 2021

Hellow
Why use it
KeyDerivator keyDerivator =
new PBKDF2KeyDerivator(new HMac(new SHA1Digest(), 64));
The decrypted data is preceded by IV

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