using System;

using System.Linq;

using System.Security.Cryptography;

using System.Text;

using Sodium;

public static class Program

{

    public static void Main()

    {

            var encPass = GenerateEncPassword("db3d8e1f4ea2", "8dd9aad29d9a614c338cff479f850d3ec57c525c33b3f702ab65e9e057fc087e", "87", "9");

            Console.WriteLine(encPass);

    }

    public static string GenerateEncPassword(string password, string publicKey, string keyId, string version)

        {

            var time = DateTime.UtcNow.ToTimestamp(); // Unix timestamp

            var keyBytes = publicKey.HexToBytes(); // Convert a hex string to a byte array

            var key = new byte[32];

            new Random().NextBytes(key);

            var iv = new byte[12];

            var tag = new byte[16];

            var plainText = Encoding.UTF8.GetBytes(password);//.ToBytes(); // ToBytes = Encoding.UTF8.GetBytes

            var cipherText = new byte[plainText.Length];

​

            using (var cipher = new AesGcm(key))

            {

                cipher.Encrypt(nonce: iv,

                    plaintext: plainText,

                    ciphertext: cipherText,

                    tag: tag,

                    associatedData: Encoding.UTF8.GetBytes(time.ToString()));//.ToBytes()); // GetBytes = Encoding.UTF8.GetBytes

            }

​

            var encryptedKey = SealedPublicKeyBox.Create(key, keyBytes);

            var bytesOfLen = BitConverter.GetBytes((short)encryptedKey.Length); // ToBytes = BitConverter.GetBytes(short);

            var info = new byte[] { 1, byte.Parse(keyId) };

            var bytes = info.Concat(bytesOfLen).Concat(encryptedKey).Concat(tag).Concat(cipherText); // Concat means that concat two array

​

            // expected: #PWD_INSTAGRAM_BROWSER:10:1595671654:ARBQAFWLYGkTT9UU0dyUCkaGTRFu0PH5Ph5s86DUAbZ+B9xon8cKmnqQGaUo7bB4NHCMKQRY69b9LwaJZ1rDw1OFM0LEGtI+KbDuDC0QnfJM6o1no0XPOl73RJoUZ/OfN5nE2q/IdqX0NFinS0faRf8=

            var str = $"#PWD_INSTAGRAM_BROWSER:{version}:{time}:{Convert.ToBase64String(bytes)}"; // ToBase64 = Convert.ToBase64String

            return str;

        }

​

        public static byte[] HexToBytes(this string hex)

        {

            return Enumerable.Range(0, hex.Length / 2)

                .Select(x => Convert.ToByte(hex.Substring(x * 2, 2), 16))

                .ToArray();

        }

​

        public static T[] Concat<T>(this T[] x, T[] y)

        {

            var z = new T[x.Length + y.Length];

            x.CopyTo(z, 0);

            y.CopyTo(z, x.Length);

            return z;

        }

​

        private static readonly DateTime _jan1St1970 = new DateTime(1970, 1, 1, 0, 0, 0, DateTimeKind.Utc);

        public static long ToTimestamp(this DateTime d)

        {

            return (long)(d.ToUniversalTime() - _jan1St1970).TotalSeconds;

        }

}