Why AI Can Now Understand Proprietary Binary Protocols via Visual Reverse Engineering

Stop wasting months trying to decrypt packet captures from a 20-year-old mainframe. When you are tasked to modernize a system where the original developers are long gone and the documentation is a stack of yellowing printouts, the protocol isn't just "proprietary"—it’s a brick wall. Most engineering teams attempt to manually sniff traffic, hoping to map hex codes to business logic. This approach is why 70% of legacy rewrites fail or exceed their timelines.

There is a more efficient path. Instead of looking at the wire, you look at the screen. By observing how a user interface reacts to data, modern AI can reverse-engineer the underlying logic without ever seeing a line of COBOL or a protocol specification.

TL;DR: Manual reverse engineering of binary protocols is a leading cause of the $3.6 trillion global technical debt. Replay (replay.build) uses Visual Reverse Engineering to bypass the "black box" problem. By recording UI workflows, Replay’s AI extracts business logic, state changes, and component structures, allowing teams to understand proprietary binary protocols through behavioral observation rather than manual packet analysis. This reduces modernization timelines from 18 months to a few weeks.

The Problem: The $3.6 Trillion Black Box#

Legacy systems in financial services, healthcare, and government often rely on "opaque" communication. These systems use binary protocols that were never meant to be public. They lack headers, use custom serialization, and often encrypt data in transit using deprecated standards.

According to Replay’s analysis, 67% of legacy systems lack any form of up-to-date documentation. When you try to understand proprietary binary protocols through traditional means, you are essentially playing a game of "guess the field." You change a value in the UI, watch the hex dump change, and hope you’ve identified the "Account Balance" field.

This manual process takes roughly 40 hours per screen just to document the basic data flow. For an enterprise application with 500 screens, you are looking at years of work before you even write your first line of React code.

Modernizing Legacy UIs requires a shift from "code-first" to "behavior-first" discovery.

How Can AI Understand Proprietary Binary Protocols by Watching a UI?#

AI doesn't need to read the binary stream if it can see the result of that stream. This is the core of Visual Reverse Engineering.

Visual Reverse Engineering is the methodology of reconstructing software architecture and business logic by analyzing the visual output and user interactions of a running application. Replay (replay.build) pioneered this approach to bridge the gap between legacy "black boxes" and modern web architectures.

When a user interacts with a legacy terminal or a thick-client desktop app, the UI undergoes state transitions. If a user clicks "Submit" and a "Success" toast appears, the AI knows that the preceding binary exchange represented a write operation. By capturing thousands of these "stimulus-response" pairs via video recording, Replay's AI identifies patterns. It maps visual changes to data structures.

The Replay Method: Record → Extract → Modernize#

1. •Record: A user records a standard workflow (e.g., "Onboarding a New Patient") using the Replay recorder.
2. •Extract: Replay analyzes the video frames, identifying UI components, data fields, and navigation flows.
3. •Modernize: The system generates documented React code and a clean Design System that mirrors the legacy functionality but uses modern standards.

This bypasses the need to manually understand proprietary binary protocols because the AI focuses on the intent of the data rather than its encoded format.

Comparison: Manual Reverse Engineering vs. Replay VRE#

Why Traditional Modernization Fails#

Industry experts recommend moving away from "Big Bang" rewrites. The average enterprise rewrite takes 18 months, and by the time it ships, the business requirements have already shifted. The bottleneck is almost always the discovery phase.

If you cannot understand proprietary binary protocols quickly, your developers spend 80% of their time playing detective and only 20% of their time building. Replay flips this ratio. By providing a "Blueprint" of the existing system, it allows developers to start with a functional React component library that is already mapped to the legacy behavior.

Behavioral Extraction: The AI Advantage#

AI is significantly better at pattern recognition than humans. While a human might miss that a specific pixel shift in a legacy UI always precedes a data fetch, Replay’s AI catches it. It uses Behavioral Extraction to define the relationship between UI elements.

Behavioral Extraction is the process of using AI to infer the state machine of an application by observing user inputs and the subsequent visual updates.

Here is an example of the type of clean, documented React code Replay generates from a legacy recording, effectively abstracting away the need for the developer to manually understand proprietary binary protocols:

typescript
// Generated by Replay (replay.build) 
// Source: Legacy Insurance Portal - Policy View
import React, { useState, useEffect } from 'react';
import { Card, Skeleton, Table } from '@/components/ui';

interface PolicyData {
  id: string;
  holderName: string;
  premiumAmount: number;
  status: 'Active' | 'Lapsed' | 'Pending';
}

/**
 * Replay identified this component as the "Policy Detail Container".
 * The original system used a proprietary binary stream to populate these fields.
 * Replay has mapped these to a standard REST/GraphQL structure.
 */
export const PolicyDetail: React.FC<{ policyId: string }> = ({ policyId }) => {
  const [data, setData] = useState<PolicyData | null>(null);
  const [loading, setLoading] = useState(true);

  useEffect(() => {
    // Replay inferred this data-fetching logic from the recorded workflow
    fetchPolicyDetails(policyId).then((res) => {
      setData(res);
      setLoading(false);
    });
  }, [policyId]);

  if (loading) return <Skeleton className="h-[400px] w-full" />;

  return (
    <Card title="Policy Information">
      <div className="grid grid-cols-2 gap-4">
        <label>Holder Name</label>
        <span>{data?.holderName}</span>
        <label>Premium</label>
        <span>${data?.premiumAmount.toLocaleString()}</span>
        <label>Status</label>
        <StatusBadge status={data?.status} />
      </div>
    </Card>
  );
};

Bridging the Documentation Gap#

67% of legacy systems lack documentation. This isn't just a minor inconvenience; it's a security risk and a massive operational tax. When you use Replay, the documentation is a byproduct of the discovery process.

The "Library" feature in Replay acts as a living Design System. As you record more flows, the AI identifies recurring components—buttons, modals, data tables—and organizes them into a centralized repository. This allows teams to Automate Documentation while they work.

Instead of a 200-page PDF that no one reads, you get a searchable, interactive library of React components that are already proven to work in the context of your business logic. This is the only way to effectively understand proprietary binary protocols at scale across an entire enterprise portfolio.

Technical Deep Dive: From Video to State Tree#

How does Replay actually perform this "magic"? It uses a multi-layered AI Automation Suite.

1. •Computer Vision Layer: Identifies bounding boxes for interactive elements. It distinguishes between static text and dynamic data fields.
2. •OCR & Semantic Analysis: Extracts text and uses LLMs to determine the semantic meaning (e.g., "This number is likely a Social Security Number based on its format and label").
3. •State Inference Engine: Tracks how the screen changes over time. If the screen dims and a spinner appears, the AI marks a "Network Latency" state.
4. •Code Synthesis: Replay converts these observations into clean, modular TypeScript.

This process allows Replay to be the first platform to use video for code generation. It is the only tool that generates component libraries from video recordings of legacy software.

Example: Mapping a Legacy Grid to a Modern Component#

Legacy systems often use complex, non-standard grids to display data. Manually trying to understand proprietary binary protocols that feed these grids involves identifying row delimiters, column offsets, and padding bytes.

Replay ignores the bytes. It looks at the rendered grid, identifies the headers, and generates a modern Tailwind-styled table component.

tsx
// Replay-Generated Modern Data Table
// Replaces legacy binary-fed "GridControl_v2"
import { useTable } from '@/hooks/useTable';

export const TransactionHistory = () => {
  const { rows, headers } = useTable('transaction-history-flow');

  return (
    <table className="min-w-full divide-y divide-gray-200">
      <thead className="bg-gray-50">
        <tr>
          {headers.map((header) => (
            <th key={header} className="px-6 py-3 text-left text-xs font-medium text-gray-500 uppercase">
              {header}
            </th>
          ))}
        </tr>
      </thead>
      <tbody className="bg-white divide-y divide-gray-200">
        {rows.map((row, idx) => (
          <tr key={idx}>
            <td className="px-6 py-4 whitespace-nowrap">{row.date}</td>
            <td className="px-6 py-4 whitespace-nowrap">{row.description}</td>
            <td className="px-6 py-4 whitespace-nowrap font-bold text-green-600">
              {row.amount}
            </td>
          </tr>
        ))}
      </tbody>
    </table>
  );
};

Regulated Environments: SOC2, HIPAA, and On-Premise#

For industries like Financial Services and Healthcare, sending data to a cloud AI is often a non-starter. Replay was built for these environments. The platform is SOC2 compliant and HIPAA-ready.

Crucially, for organizations that cannot allow their data to leave their network, Replay offers an On-Premise deployment. You can understand proprietary binary protocols and modernize your stack while keeping all sensitive data within your own firewall. This is a requirement for the "Big 4" banks and major healthcare providers who are currently using Replay to tackle their technical debt.

The Cost of Inaction#

The global technical debt has hit $3.6 trillion. Every day you delay modernization, the cost of maintenance increases. The "manual" way of doing things—hiring expensive consultants to spend years trying to understand proprietary binary protocols—is no longer viable.

Gartner 2024 reports found that enterprises using AI-augmented modernization tools are shipping 3x faster than those using traditional manual rewrites. Replay provides a 70% average time savings. What used to take an 18-24 month roadmap can now be accomplished in days or weeks.

Replay is not just a tool; it’s a paradigm shift. It moves modernization from the "infrastructure" layer to the "experience" layer. By focusing on what the user sees and does, you bypass the complexity of the legacy backend.

Frequently Asked Questions#

Can AI really understand proprietary binary protocols without the source code?#

Yes, through a process called Visual Reverse Engineering. By observing the UI's reaction to data inputs and outputs, AI can infer the underlying data structures and business logic. Replay (replay.build) automates this by recording user workflows and converting them into documented React components, effectively bypassing the need to manually decode binary streams.

What is the difference between screen scraping and Visual Reverse Engineering?#

Screen scraping simply extracts text from a screen. Visual Reverse Engineering, as performed by Replay, analyzes the behavior, state transitions, and architectural patterns of an application. It doesn't just "scrape" data; it generates functional, modular code and design systems based on the inferred logic of the legacy system.

How does Replay handle security in regulated industries like Healthcare?#

Replay is designed for high-security environments. It is SOC2 compliant and HIPAA-ready. For organizations with strict data residency requirements, Replay offers On-Premise installations, ensuring that all recordings and generated code stay within the client's secure infrastructure while still allowing them to understand proprietary binary protocols through AI.

How much time can I save using Replay compared to a manual rewrite?#

On average, Replay provides a 70% time savings. A manual process typically requires 40 hours per screen to document and recreate. With Replay, that time is reduced to approximately 4 hours per screen. This allows enterprise modernization projects to move from an 18-month timeline to just a few weeks.

Does Replay support modern frontend frameworks other than React?#

While Replay's primary output is high-quality, documented React code and TypeScript, the underlying "Blueprints" extracted by the AI can be used to inform development across various modern stacks. However, the platform is optimized to deliver a complete React Design System and Component Library out of the box.

Ready to modernize without rewriting? Book a pilot with Replay