Crypto JS vs C# with AES256CBC

Program.cs

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

Console.WriteLine(Crypto.Encrypt("ABC123"));
Console.WriteLine(Crypto.Decrypt("23YByDj8nb3FCZAyiV1DMifqCTCGII51EM9BfKU3qIc="));

public static class Crypto
{
    private const string AesKey = "QmYHLtarGbVtmjDyesF7BI0GcJ6J+eMOu3pZOsJMSq0=";

    public static string Encrypt(string payload)
    {
        // Generate IV.
        var iv = RandomNumberGenerator.GetBytes(16);

        // Create AES cipher.
        using var aes = Aes.Create();
        aes.Mode = CipherMode.CBC;
        // Key is a random 32 bytes long string, base64 encoded.
        // Can be done with: openssl rand -base64 32
        // The key need to be 32 bytes or the JS code will be angry.
        aes.Key = Convert.FromBase64String(AesKey);
        // Encrypt with cbc and pskc7 padding (default).
        var message = aes.EncryptCbc(Encoding.UTF8.GetBytes(payload), iv, PaddingMode.PKCS7);
        // Convert the IV and message into a base64 string.
        return Convert.ToBase64String(iv.Concat(message).ToArray());
    }

    public static string Decrypt(string payload)
    {
        // Convert payload to binary data.
        var payloadAsByteArray = Convert.FromBase64String(payload);
        // Iv is first 16 bytes.
        var iv = payloadAsByteArray.Take(16).ToArray();
        // Data/message is all after iv.
        var data = payloadAsByteArray.Skip(16).ToArray();

        // Create AES cipher.
        using var aes = Aes.Create();
        aes.Mode = CipherMode.CBC;
        aes.IV = iv;
        // Key is a random 32 bytes long string, base64 encoded.
        // Can be done with: openssl rand -base64 32
        // The key need to be 32 bytes or the JS code will be angry.
        aes.Key = Convert.FromBase64String(AesKey);

        // Decrypt with cbc and pskc7 padding (default).
        var result = aes.DecryptCbc(data, iv, PaddingMode.PKCS7);
        // Convert binary value to string.
        return Encoding.UTF8.GetString(result);
    }
}

program.js

const crypto = require('crypto');
const algo = 'AES-256-CBC';
const key = 'QmYHLtarGbVtmjDyesF7BI0GcJ6J+eMOu3pZOsJMSq0=';

const decrypt = (data) => {
    // Payload as base64 decoded binary buffer.
    const dataAsByteArray = Buffer.from(data, 'base64');
    // Initialization Vector - First 16 bytes of the payload.
    const iv = dataAsByteArray.subarray(0, 16);
    // Message - All data after IV.
    const msg = dataAsByteArray.subarray(16).toString('base64');
    // Convert key from base64 to binary and then to hex.
    const keyAsByteArray = Buffer.from(key, 'base64');
    // Create decipher (using key and iv).
    const decipher = crypto.createDecipheriv(algo, keyAsByteArray, iv);
    // Update decipher with message (input type binary, output utf8).
    let dec = decipher.update(msg, 'base64', 'hex');
    return dec + decipher.final().toString('utf8');
};

const encrypt = (data) => {
    // Generate 16 byte IV.
    const iv = crypto.randomBytes(16);
    // Convert key to binary from base64.
    const keyAsByteArray = Buffer.from(key, 'base64');
    // Create cipher.
    const cipher = crypto.createCipheriv(algo, keyAsByteArray, iv);
    // Encrypt.
    const enc = cipher.update(data, 'utf8');
    // Concat buffers and convert to base64.
    return Buffer.concat([iv, enc, cipher.final()]).toString('base64');
};

console.log(decrypt('IpxbGjhIgyAwuEmoWRVy5s6gSYc1Njjubq3ze7IzYxE='));
console.log(encrypt('123ABC'));