mybd-cryfs

mybd-cryfs is a cursor rule for Cursor from bigdata2211it-web/ai-vault-skills. It costs 67 tokens per session (3,320 once invoked), scanned D, original, MIT.

An encrypted folder for storing credentials and other secrets using CryFS, a tool that shows decrypted files only while the vault is open.

In plain words
What is it for?
Use it to set up, open, close, migrate, back up, and troubleshoot a CryFS credentials vault across operating systems.
Why use it?
It keeps secret files unreadable on disk and can hide them again after inactivity. It also helps prevent an agent from reading them until a person explicitly opens the vault.

Cursor rule for Cursor

Written for Cursor: a Cursor rule (.mdc). Also seen: mentions AGENTS.md.

Good fit Use it to set up, open, close, migrate, back up, and troubleshoot a CryFS credentials vault across operating systems.

Compare 6 cursor rules from other repositories ↓
Install with agentmods
npx agentmods add rules/bigdata2211it-web/ai-vault-skills/mybd-cryfs
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.

Clone the repo
git clone --depth 1 https://github.com/bigdata2211it-web/ai-vault-skills

Made for: Cursor.

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 mybd-cryfs

README.md
[![agentmods](https://agentmods.dev/badge/rules/bigdata2211it-web/ai-vault-skills/mybd-cryfs/github.svg)](https://agentmods.dev/rules/bigdata2211it-web/ai-vault-skills/mybd-cryfs)
Your own site
<a href="https://agentmods.dev/rules/bigdata2211it-web/ai-vault-skills/mybd-cryfs"><img src="https://agentmods.dev/badge/rules/bigdata2211it-web/ai-vault-skills/mybd-cryfs/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 mybd-cryfs

Your own site · 80×15
<a href="https://agentmods.dev/rules/bigdata2211it-web/ai-vault-skills/mybd-cryfs"><img src="https://agentmods.dev/badge/rules/bigdata2211it-web/ai-vault-skills/mybd-cryfs.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 67 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 3,320 The whole file, excluding the scripts and references it only reads on demand.
Security scan D 2 findings. A grade says what 26 rules found in the file — not that it is safe.
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 $0.00067 $0.03320
Opus 5 $0.00034 $0.01660
Sonnet 5 $0.00013 $0.00664
Haiku 4.5 $0.00007 $0.00332

Measured 9d ago against content hash 7898195743c8, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-09, from the pricing page.

Security

Grade D, and why

mybd-cryfs scanned grade D with 2 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 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.

Asks for rootmediumPrivilege escalation

A mod that escalates privileges can change anything on the machine, not only the project.

sudo apt update && sudo apt install cryfs

Recursive force deletehighDestructive command

rm -rf with a variable or a broad path is one typo away from removing the wrong tree.

rm -rf ~/secrets
cursor/mybd-cryfs/mybd-cryfs.mdc · 344 lines

How it starts

The opening of the file, as written. The whole thing — 344 lines — stays where its author put it; the contents beside it link to each section on GitHub.

mybd-cryfs — encrypted credentials vault with cryfs

Goal

Keep a folder of secrets (logins/passwords/TSV/JSON) encrypted at rest, usable on demand after entering a password, and auto-locked when idle. Works for a human and for an AI agent working under the human's explicit permission.

Threat model

Threat Covered
Another user/process reads plaintext files Yes — ciphertext on disk only
AI agent reads secrets without permission Yes — mountpoint empty until human opens
Disk theft Yes — ciphertext useless without password
Password leaks via logs/history Mitigated — pass via stdin/env, not config
Forgot to close Yes — --unmount-idle N auto-unmounts
Forgot password No recovery — AES/XChaCha key is derived from password
Disk failure without backup No recovery — keep an external backup of the cipher dir

How cryfs works

  • Backend dir holds encrypted blocks (hex-named) + cryfs.config.
  • cryfs.config stores the encryption key, itself encrypted by your password (scrypt KDF).
  • Mounting decrypts the key, FUSE presents a plaintext view at the mountpoint.
  • Unmounting drops the plaintext view; ciphertext stays on disk.
  • Default cipher: xchacha20-poly1305 (AEAD). Block size 16 KiB.
  • File names, directory structure, sizes — all encrypted, nothing leaks.

Install

Linux — Debian/Ubuntu/Mint

sudo apt update && sudo apt install cryfs

Linux — Fedora/RHEL

sudo dnf install cryfs

If not in repos, use the upstream AppImage or build from source (see https://github.com/cryfs/cryfs).

Linux — Arch/Manjaro

sudo pacman -S cryfs

AUR alternative: cryfs-git.

Linux — NixOS

# configuration.nix
environment.systemPackages = with pkgs; [ cryfs ];
# FUSE is usually enabled; otherwise:
# boot.extraModulePackages = [ ];

Linux — Alpine

sudo apk add cryfs fuse
# ensure /dev/fuse exists and user is in the fuse/group that owns /dev/fuse

Read the full file on GitHub · 344 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 · 344 lines · 67 tokens per session scan D 7898195743c8

Subscribe to this mod's changes

mybd-cryfs is a cursor rule published in the GitHub repository bigdata2211it-web/ai-vault-skills (2 stars, last pushed 2mo ago), licensed MIT. It adds 67 tokens to every session and 3,320 once invoked, about $0.0003 per session on Opus 5. A static security scan graded it D with 2 findings (asks for root, recursive force delete). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.