Encrypt in php and decrypt in Dart(flutter)

Here is a method for encrypting/decrypting in Flutter, PHP and C# using AES-256-CBC algorithm.

AES-256 is considered quantum-safe.

Flutter:

Include the package https://pub.dev/packages/encrypt

import 'dart:convert';

import 'package:encrypt/encrypt.dart';
import 'package:crypto/crypto.dart';

class Encryption {
  static final Encryption instance = Encryption._();
  
  late IV _iv;
  late Encrypter _encrypter;

  Encryption._() {
    const mykey = 'ThisIsASecuredKey';
    const myiv = 'ThisIsASecuredBlock';
    final keyUtf8 = utf8.encode(mykey);
    final ivUtf8 = utf8.encode(myiv);
    final key = sha256.convert(keyUtf8).toString().substring(0, 32);
    final iv = sha256.convert(ivUtf8).toString().substring(0, 16);
    _iv = IV.fromUtf8(iv);

    _encrypter = Encrypter(AES(Key.fromUtf8(key), mode: AESMode.cbc));
  }

  String encrypt(String value) {
    return _encrypter.encrypt(value, iv: _iv).base64;
  }

  String decrypt(String base64value) {
    final encrypted = Encrypted.fromBase64(base64value);
    return _encrypter.decrypt(encrypted, iv: _iv);
  }
}

Usage (Singleton Class):

var encrypted = Encryption.instance.encrypt('my value to be encrypted');
var decrypted = Encryption.instance.decrypt(encrypted);

PHP:

<?php

class Encryption
{
    private string $encryptMethod = 'AES-256-CBC';
    private string $key;
    private string $iv;

    public function __construct()
    {
        $mykey = 'ThisIsASecuredKey';
        $myiv = 'ThisIsASecuredBlock';
        $this->key = substr(hash('sha256', $mykey), 0, 32);
        $this->iv = substr(hash('sha256', $myiv), 0, 16);
    }

    public function encrypt(string $value): string
    {
        return openssl_encrypt(
            $value,
            $this->encryptMethod,
            $this->key,
            0,
            $this->iv
        );
    }

    public function decrypt(string $base64Value): string
    {
        return openssl_decrypt(
            $base64Value,
            $this->encryptMethod,
            $this->key,
            0,
            $this->iv
        );
    }
}

Usage:

$encryption = new Encryption();
$encrypted = $encryption->encrypt('my value to be encrypted');
$decrypted = $encryption->decrypt($encrypted);

C#:

using System;
using System.IO;
using System.Security.Cryptography;
using System.Text;

public class Encryption
{
    byte[] key;
    byte[] iv;

    private Encryption instance;
    public Encryption Instance
    {
        get
        {
            if (instance == null)
                instance = new Encryption();
            return instance;
        }
    }

    private Encryption()
    {
        var Key = "ThisIsASecuredKey";
        var Iv = "ThisIsASecuredBlock";

        using (var sha256 = SHA256.Create())
        {
            key = Encoding.UTF8.GetBytes(
                 ToHex(sha256.ComputeHash(Encoding.UTF8.GetBytes(Key)))
                    .Substring(0, 32)
            );
            iv = Encoding.UTF8.GetBytes(
                 ToHex(sha256.ComputeHash(Encoding.UTF8.GetBytes(Iv)))
                    .Substring(0, 16)
            );
        }
    }
    
    public string Encrypt(string input)
    {
        using (var aesManaged = new AesManaged())
        using (var ms = new MemoryStream())
        {
            using (var cs = new CryptoStream(
                ms,
                aesManaged.CreateEncryptor(key, iv),
                CryptoStreamMode.Write
            ))
            {
                var inputBytes = Encoding.UTF8.GetBytes(input);
                cs.Write(inputBytes, 0, inputBytes.Length);
            }

            return Convert.ToBase64String(ms.ToArray());
        }
    }

    public string Decrypt(string base64value)
    {
        using (var aesManaged = new AesManaged())
        using (var decryptor = aesManaged.CreateDecryptor(key, iv))
        using (var ms = new MemoryStream(Convert.FromBase64String(base64value)))
        using (var cs = new CryptoStream(ms, decryptor, CryptoStreamMode.Read))
        using (var sr = new StreamReader(cs))
        {
            return sr.ReadToEnd();
        }
    }

    private string ToHex(byte[] bytes, bool upperCase = false)
    {
        var result = new StringBuilder(bytes.Length * 2);
        for (int i = 0; i < bytes.Length; i++)
            result.Append(bytes[i].ToString(upperCase ? "X2" : "x2"));
        return result.ToString();
    }
}

Usage (Singleton Class):

var encrypted = Encryption.Instance.Encrypt("my value to be encrypted");
var decrypted = Encryption.Instance.Decrypt(encrypted);

You can use AES encrypt/decrypt that supported on both sides.

flutter_string_encryption

PHP

You can use Cipher2 library for cryptography in flutter with the help of library you can encrypt and decrypt string with "aes-128-cbc" method

    //Make sure you import the library, stringEncryption is a user define function you can define your own
    stringEncryption() async { //call this method 
    String plainText ='String to encrypt';
    String key = '1245714587458745'; //combination of 16 character
    String iv = 'e16ce913a20dadb8'; ////combination of 16 character
    String encryptedString =
    await Cipher2.encryptAesCbc128Padding7(plainText, key, iv);
    print("key:$key");
    print("iv:$iv");
    print("String:$encryptedString");

    //for decrypt use decrypt function 
    decryptedString = await Cipher2.decryptAesCbc128Padding7(encryptedString, key, iv);
    //parameters: encryptedString,sameKey,SameIv
    }

    //To decrypt in PHP
    $method = 'aes-128-cbc';
    $decryptedString = openssl_decrypt("encryptedString", $method, "SameKeyUsedInFlutter", 0, "SameIvUsedInFlutter");

    //To encrypt in PHP
    $encryptedString = openssl_encrypt("Text to encrypt", $method, "SameKeyUsedInFlutter", 0, "SameIvUsedInFlutter");
    //Key and IV must need to match

function CryptoJSAesDecrypt(passphrase,encrypted_json_string){

var obj_json = JSON.parse(encrypted_json_string);

var encrypted = obj_json.ciphertext;
var salt = CryptoJS.enc.Hex.parse(obj_json.salt);
var iv = CryptoJS.enc.Hex.parse(obj_json.iv);   

var key = CryptoJS.PBKDF2(passphrase, salt, { hasher: CryptoJS.algo.SHA512, keySize: 64/8, iterations: 999});


var decrypted = CryptoJS.AES.decrypt(encrypted, key, { iv: iv});

return decrypted.toString(CryptoJS.enc.Utf8);

} i want to covert php func crypto to flutter