Instagram enc_password generator in C#

encrypt.cs

// Packages need to be installed: 
// Sodium.Core
// System.Security.Cryptography.Algorithms

// The values of publicKey,keyId,version are from shared_data.
// You need to call https://www.instagram.com/data/shared_data/ to get shared_data first
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 = 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: time.ToString().ToBytes()); // GetBytes = Encoding.UTF8.GetBytes
    }

    var encryptedKey = SealedPublicKeyBox.Create(key, keyBytes);
    var bytesOfLen = ((short)encryptedKey.Length).ToBytes(); // 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}:{bytes.ToBase64()}"; // 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;
}