competition-zip-archive

competition-zip-archive is a skill for Codex from zhaoxuya520/reverse-skill. It costs 112 tokens per session (1,276 once invoked), scanned A, original, MIT.

A workflow for CTF challenges involving ZIP archives, including older password protection called ZipCrypto. It uses predictable file content when available to recover keys and extract the archive.

In plain words
What is it for?
It helps preserve and identify an archive, list its files, determine its encryption type, build a known-content candidate, recover ZipCrypto keys, and extract the result.
Why use it?
It focuses the investigation on the archive’s actual format and recoverable evidence instead of starting with blind password guessing.

Skill for Codex

Written for Codex: agents/openai.yaml present. Also seen: $skill-name invocation.

Needs its repository: it runs a file that does not travel with it, so clone the repository first. The line is bash kali/scripts/bootstrap-reverse.sh bkcrack.

Good fit It helps preserve and identify an archive, list its files, determine its encryption type, build a known-content candidate, recover ZipCrypto keys, and extract the result.

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About the project

Reverse Skill is a routing package for AI coding agents that selects appropriate reverse-engineering, penetration-testing, and security-research methods and tools for a given target. It is used for tasks involving APKs, binaries, frontend JavaScript, packet captures, CTF challenges, and authorized penetration testing. Its catalogue add-ons provide the skills and instructions that guide these workflows.

zhaoxuya520/reverse-skill · 35,402 stars · on GitHub

Install

Getting it into your agent

It runs from inside its repository, so the clone comes first — what it calls does not travel with the file alone.

Clone the repo
git clone --depth 1 https://github.com/zhaoxuya520/reverse-skill
agentmods
npx agentmods add skills/zhaoxuya520/reverse-skill/competition-zip-archive

Made for: Codex.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for competition-zip-archive

README.md
[![agentmods](https://agentmods.dev/badge/skills/zhaoxuya520/reverse-skill/competition-zip-archive/github.svg)](https://agentmods.dev/skills/zhaoxuya520/reverse-skill/competition-zip-archive)
Your own site
<a href="https://agentmods.dev/skills/zhaoxuya520/reverse-skill/competition-zip-archive"><img src="https://agentmods.dev/badge/skills/zhaoxuya520/reverse-skill/competition-zip-archive/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for competition-zip-archive

Your own site · 80×15
<a href="https://agentmods.dev/skills/zhaoxuya520/reverse-skill/competition-zip-archive"><img src="https://agentmods.dev/badge/skills/zhaoxuya520/reverse-skill/competition-zip-archive.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 112 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,276 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe. Third-party audits
  • Snyk pass 7 Sept 2026
  • NVIDIA SkillSpector pass 7 Sept 2026
How audits are shown
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5.1 $0.00112 $0.01276
Opus 5 $0.00056 $0.00638
Sonnet 5 $0.00022 $0.00255
Haiku 4.5 $0.00011 $0.00128

Measured 11d ago against content hash e2f86fcfded2, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-10, from the pricing page.

Security

Grade A, and why

competition-zip-archive scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 11d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

CTF-Sandbox-Orchestrator/competition-zip-archive/SKILL.md · 109 lines

How it starts

The opening of the file, as written. The whole thing — 109 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Competition ZIP Archive

Use this skill only as a downstream specialization after $ctf-sandbox-orchestrator is active and has established sandbox assumptions, evidence priorities, and the analysis project root. If that has not happened yet, return to $ctf-sandbox-orchestrator first.

Use this skill when the decisive path is an encrypted ZIP/PKZIP archive rather than an upload parser or a generic crypto blob. Prefer the legacy ZipCrypto known-plaintext path when the challenge gives a predictable file, format header, template, or other recoverable plaintext. Do not begin with blind password brute force.

Reply in Simplified Chinese unless the user explicitly requests English. Keep commands and tool output in their original form.

Quick Start

  1. Preserve the original archive, compute a hash, and work on a copy under the analysis project's work/<case>/ directory.
  2. Confirm the actual archive format and list entries before attempting a password attack.
  3. Determine whether the entry uses legacy ZipCrypto. bkcrack does not recover WinZip AES or other modern encryption.
  4. Build an exact known-plaintext candidate. The attack needs at least 12 known plaintext bytes, including at least 8 contiguous bytes.
  5. Recover the internal keys with bkcrack, then create an unencrypted copy and extract it.
  6. Preserve the command, entry names, known-plaintext source, recovered keys, output hash, and final flag as evidence.

Tool Setup

Use the normal tool index and bootstrap path before guessing an executable location:

powershell -NoProfile -ExecutionPolicy Bypass -File skills/scripts/refresh-tool-index.ps1
powershell -NoProfile -ExecutionPolicy Bypass -File skills/scripts/bootstrap-reverse.ps1 -Capability bkcrack

On Kali, use the equivalent capability command:

bash kali/scripts/bootstrap-reverse.sh bkcrack

The Windows capability is pinned to the v1.8.1 release and verifies the GitHub asset digest. If the tool is installed manually, refresh skills/tool-index.md afterward.

Read the full file on GitHub · 109 lines

Files

What ships with it

2 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 11d ago First seen · 109 lines · 112 tokens per session scan A e2f86fcfded2

Subscribe to this mod's changes

competition-zip-archive is a skill published in the GitHub repository zhaoxuya520/reverse-skill (35,402 stars, last pushed 7d ago), licensed MIT. It adds 112 tokens to every session and 1,276 once invoked, about $0.0006 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

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