crypto-decode

crypto-decode is a skill for Claude Code, Codex from PurpleAILAB/Decepticon. It costs 30 tokens per session (1,463 once invoked), scanned A, original, Apache-2.0.

A guide to identifying and decoding unknown encrypted, encoded, or hashed text. It explains how to recognise common formats and choose tools for tasks such as Base64 decoding, classical-cipher analysis, and hash identification.

In plain words
What is it for?
Use it to detect formats, unwrap multiple encoding layers, identify hash types, test common cipher families, convert representations, and analyse JWT, hexadecimal, Base64, and similar values.
Why use it?
It reduces guesswork when a token, database field, captured payload, or puzzle value is not immediately recognisable.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one. Also seen: positional $N argument.

Good fit Use it to detect formats, unwrap multiple encoding layers, identify hash types, test common cipher families, convert representations, and analyse JWT, hexadecimal, Base64, and similar values.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/purpleailab/decepticon/crypto
About the project

Decepticon is an autonomous red-team agent that coordinates AI agents, security tools, sandboxes, and supporting services for authorized cybersecurity assessments. Security researchers and red teams can run it through its Docker stack, cloud service, command-line interface, or Python SDK, with the catalogue entries representing its available skills.

PurpleAILAB/Decepticon · 5,491 stars · on GitHub · decepticon.red

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

Any agent
npx skills add PurpleAILAB/Decepticon --skill crypto
Clone the repo
git clone --depth 1 https://github.com/PurpleAILAB/Decepticon

Made for: Claude Code, 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 crypto-decode

README.md
[![agentmods](https://agentmods.dev/badge/skills/purpleailab/decepticon/crypto/github.svg)](https://agentmods.dev/skills/purpleailab/decepticon/crypto)
Your own site
<a href="https://agentmods.dev/skills/purpleailab/decepticon/crypto"><img src="https://agentmods.dev/badge/skills/purpleailab/decepticon/crypto/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 crypto-decode

Your own site · 80×15
<a href="https://agentmods.dev/skills/purpleailab/decepticon/crypto"><img src="https://agentmods.dev/badge/skills/purpleailab/decepticon/crypto.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 30 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,463 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 1 finding. A grade says what 26 rules found in the file — not that it is safe. Third-party audits
  • NVIDIA SkillSpector warn 7 Sept 2026
SkillSpector: 1 finding, up to high

These are SkillSpector’s own severities. On a checked sample its high-severity flags on skills were ~96% false positives — a documented command, a public API, a “never do X” rule — so we show them as a caution to read, not a verdict. Why →

  • high YARA Match · line 101
    YARA rule matched a hack tool or exploit indicator (offensive tools, reconnaissance, privilege escalation, or exploit frameworks).
    Fix: Remove offensive tool references and exploit code. Legitimate agent skills should not contain penetration testing tools, exploit frameworks, or reconnaissance utilities.
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 $0.00030 $0.01463
Opus 5 $0.00015 $0.00732
Sonnet 5 $0.00006 $0.00293
Haiku 4.5 $0.00003 $0.00146

Measured 9d ago against content hash 4e755e1170f4, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-12, from the pricing page.

Security

Grade A, and why

crypto-decode scanned grade A with 1 finding 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 9d 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.

Runs shell commandslowCapability

Expected in a hook, worth knowing in a rule or an instructions file.

r = subprocess.run(cmd, timeout=timeout, capture_output=True, text=True)
Origin

Copies of this mod

1 near-identical copy found in the catalogue:

packages/decepticon/decepticon/skills/standard/exploit/crypto/SKILL.md · 162 lines

How it starts

The opening of the file, as written. The whole thing — 162 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Crypto / Decode Playbook

When you have unknown ciphertext (CTF flag, leaked DB field, captured token, encoded payload), the right tool depends on the cipher class.

1. Identify FIRST

Unknown text → automated cracker

# Ciphey — original (Python, slowed maintenance)
ciphey -t "$CIPHERTEXT"

# Ares — Rust rewrite (faster, current)
ares -t "$CIPHERTEXT"

A*-search across 16+ decoders (base64, base85, hex, Caesar, ROT-N, Atbash, Vigenere, XOR-known-plaintext, URL encoding, binary, morse, brainfuck, esolang, leetspeak, etc.) + BERT plaintext detector to know when to stop.

Hash → identify type

hashid -m '$2a$12$....'             # bcrypt 12 rounds
hashid -m '5f4dcc3b5aa765d61d8327deb882cf99'  # MD5
hash-identifier

Specific format checks

# JWT
echo $TOKEN | cut -d. -f1-2 | tr '_-' '/+' | base64 -d 2>/dev/null

# Hex → bytes
echo "$HEX" | xxd -r -p

# Base64 → bytes (handle URL-safe)
echo "$B64" | tr '_-' '/+' | base64 -d 2>/dev/null

# Multi-encoded (unwind layers)
echo "$BLOB" | base64 -d | base64 -d | xxd -r -p

2. Classical cipher quick-checks

Cipher Signature
Base64 [A-Za-z0-9+/=]+, len multiple of 4
Base32 [A-Z2-7=]+
Hex [0-9a-fA-F]+, even length
Caesar/ROT only A-Z + spaces, freq-attack ready
Vigenere A-Z, multiple-of-key-length repeating bigrams
Substitution A-Z, IC ≈ 0.066 (English)
Vernam/OTP random-looking bytes, no statistical signal
XOR fixed-key bytes w/ printable XOR'd against pattern (file headers leak)
Hill small block size, matrix-based

3. CyberChef recipe library

CyberChef (gchq.github.io/CyberChef) is the GUI workhorse but recipes can be exported as JSON and chained programmatically:

# Common chains
"From Base64 / Magic / To Hex"
"From Hex / XOR (Brute) / Magic"
"AES Decrypt(KEY) / From Hex / Strings"

CLI version: cyberchef-cli (community port).

4. Hash cracking quick-ref

Mode Hash type
0 MD5
100 SHA-1
1400 SHA-256
1700 SHA-512
1000 NTLM
13100 Kerberos TGS-REP (etype 23)
19700 Kerberos TGS-REP (etype 18)
18200 Kerberos AS-REP
16500 JWT (HS256)
3200 bcrypt
7400 sha256crypt $5$
1800 sha512crypt $6$
22000 WPA-EAPOL+PMKID
7100 macOS v10.8+ (PBKDF2-SHA512)
8200 1Password Cloud Keychain

Read the full file on GitHub · 162 lines

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. 9d ago First seen · 162 lines · 30 tokens per session scan A 4e755e1170f4

Subscribe to this mod's changes

crypto-decode is a skill published in the GitHub repository PurpleAILAB/Decepticon (5,491 stars, last pushed 13d ago), licensed Apache-2.0. It adds 30 tokens to every session and 1,463 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it A with 1 finding (runs shell commands). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-03.