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Agent skill

Nodejs Keccak256

by affaan-m in affaan-m/ECC

JavaScriptとTypeScriptにおけるEthereumハッシュバグを防ぐ。NodeのSHA3-256はNIST SHA3であり、Ethereum Keccak-256ではなく、セレクター、署名、ストレージスロット、アドレス導出を静かに破壊する。

MITAuto-check passed

Install Nodejs Keccak256

skills CLI
$ npx skills add affaan-m/ECC --skill nodejs-keccak256 -a claude-code

Project install by default; add -g for ~/.claude/skills/.

GitHub CLI
$ gh skill install affaan-m/ECC nodejs-keccak256 --agent claude-code

Project scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).

Manual copy
$ git clone --depth 1 https://github.com/affaan-m/ECC.git skills-src && mkdir -p .claude/skills && cp -r skills-src/docs/ja-JP/skills/nodejs-keccak256 .claude/skills/nodejs-keccak256 && rm -rf skills-src

Use ~/.claude/skills/ instead of .claude/skills for a personal install. The folder must contain SKILL.md.

Claude Code skills documentation · loads skills from .claude/skills/

Facts

Skill name
nodejs-keccak256
GitHub stars
276k
Token cost
~631 tokens
SKILL.md length
19 words
Files
1
Skills in repo
673
Repo updated
First seen
Licence
MIT

At a glance

JavaScriptとTypeScriptにおけるEthereumハッシュバグを防ぐ。NodeのSHA3-256はNIST SHA3であり、Ethereum Keccak-256ではなく、セレクター、署名、ストレージスロット、アドレス導出を静かに破壊する。

  • SKILL.md covers 使用するタイミング, 仕組み, 例 and ルール
  • Instructions only: no scripts, shell commands, URLs or credentials in SKILL.md

What it does

Nodejs Keccak256 is an agent skill from affaan-m/ECC. JavaScriptとTypeScriptにおけるEthereumハッシュバグを防ぐ。NodeのSHA3-256はNIST SHA3であり、Ethereum Keccak-256ではなく、セレクター、署名、ストレージスロット、アドレス導出を静かに破壊する。

Its SKILL.md is about 630 tokens, which your agent loads only when the skill is triggered. It is a single SKILL.md file with no bundled scripts.

It works with Node.js, Ethereum, JavaScript and TypeScript. The repository describes itself as: The agent harness performance optimization system. Skills, instincts, memory, security, and research-first development for Claude Code, Codex, Opencode, Cursor and beyond. The licence is MIT.

Example prompts

  • “/nodejs-keccak256”

Requirements

  • Node.js

What it can do on your machine

Read from SKILL.md and the folder at commit ef648e0. It shows what the files ask for, not the result of running them.

  • Tool permissions

    Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.

    From allowed-tools in the SKILL.md frontmatter.

  • Runs code

    No scripts in the folder and no shell commands in SKILL.md (its code samples are typescript, javascript and bash).

    From the folder's file list and the shell code blocks in SKILL.md.

  • Network

    No URLs in SKILL.md.

    From URLs in SKILL.md, links to its own repository left out.

  • Credentials

    Names no API keys, tokens, secrets or passwords.

    From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

Context cost

Nodejs Keccak256 loads about 631 tokens when it runs. Until then it costs about 36 tokens; SKILL.md has 19 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it
~36
When it runs · the whole SKILL.md, loaded when a task matches
~631

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

Auto-check passed

The automated check found no risky patterns in SKILL.md.

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.

SKILL.md

The full file from affaan-m/ECC at commit ef648e0, republished under its MIT licence (© affaan-m). 19 words, ~631 tokens.

Download SKILL.mdSave it as .claude/skills/nodejs-keccak256/SKILL.md (or your agent's skills folder).
name
nodejs-keccak256
description
JavaScriptとTypeScriptにおけるEthereumハッシュバグを防ぐ。NodeのSHA3-256はNIST SHA3であり、Ethereum Keccak-256ではなく、セレクター、署名、ストレージスロット、アドレス導出を静かに破壊する。
origin
ECC direct-port adaptation
version
1.0.0

Node.js Keccak-256

EthereumはKeccak-256を使用し、Nodeのcrypto.createHash('sha3-256')が公開するNIST標準化SHA3バリアントではない。

使用するタイミング

  • Ethereum関数セレクターやイベントトピックの計算
  • JS/TSでEIP-712、署名、Merkle、またはストレージスロットヘルパーの構築
  • Nodeのcryptoを直接使用してEthereumデータをハッシュするコードのレビュー

仕組み

2つのアルゴリズムは同じ入力に対して異なる出力を生成し、Nodeは警告しない。

javascript
import crypto from 'crypto';
import { keccak256, toUtf8Bytes } from 'ethers';

const data = 'hello';
const nistSha3 = crypto.createHash('sha3-256').update(data).digest('hex');
const keccak = keccak256(toUtf8Bytes(data)).slice(2);

console.log(nistSha3 === keccak); // false

例

ethers v6
typescript
import { keccak256, toUtf8Bytes, solidityPackedKeccak256, id } from 'ethers';

const hash = keccak256(new Uint8Array([0x01, 0x02]));
const hash2 = keccak256(toUtf8Bytes('hello'));
const topic = id('Transfer(address,address,uint256)');
const packed = solidityPackedKeccak256(
  ['address', 'uint256'],
  ['0x742d35Cc6634C0532925a3b8D4C9B569890FaC1c', 100n],
);
viem
typescript
import { keccak256, toBytes } from 'viem';

const hash = keccak256(toBytes('hello'));
web3.js
javascript
const hash = web3.utils.keccak256('hello');
const packed = web3.utils.soliditySha3(
  { type: 'address', value: '0x742d35Cc6634C0532925a3b8D4C9B569890FaC1c' },
  { type: 'uint256', value: '100' },
);
一般的なパターン
typescript
import { id, keccak256, AbiCoder } from 'ethers';

const selector = id('transfer(address,uint256)').slice(0, 10);
const typeHash = keccak256(toUtf8Bytes('Transfer(address from,address to,uint256 value)'));

function getMappingSlot(key: string, mappingSlot: number): string {
  return keccak256(
    AbiCoder.defaultAbiCoder().encode(['address', 'uint256'], [key, mappingSlot]),
  );
}
公開鍵からアドレス
typescript
import { keccak256 } from 'ethers';

function pubkeyToAddress(pubkeyBytes: Uint8Array): string {
  const hash = keccak256(pubkeyBytes.slice(1));
  return '0x' + hash.slice(-40);
}
コードベースの監査
bash
grep -rn "createHash.*sha3" --include="*.ts" --include="*.js" --exclude-dir=node_modules .
grep -rn "keccak256" --include="*.ts" --include="*.js" . | grep -v node_modules

ルール

Ethereumコンテキストでは、crypto.createHash('sha3-256')を絶対に使用しない。ethers、viem、web3、または別の明示的なKeccak実装のKeccak対応ヘルパーを使用すること。

© affaan-m, MIT. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file

Files

Just SKILL.md in docs/ja-JP/skills/nodejs-keccak256 of affaan-m/ECC.

Open the folder on GitHubat commit ef648e0

Compare with similar skills

Nodejs Keccak256 next to the 5 skills that share the most tags, products or categories with it. Stars are the repository's; “used in” counts other GitHub owners with a copy.

Nodejs Keccak256 compared with similar skills
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Nodejs Keccak256 this skillaffaan-m/ECC276k—~631Automated safety check: PassMIT
Bun DevelopmentGabrielMartinMoran/mind14812 repos~3.5kAutomated safety check: NotesMIT
Generate Release Notesteambit/bit18k—~2.2kAutomated safety check: PassCustom licence
Compromise NLP Libraryspencermountain/compromise12k—~2kAutomated safety check: PassMIT
Release Roundethereumjs/ethereumjs-monorepo2.8k—~2kAutomated safety check: PassNone
Update Est Fixturesethereumjs/ethereumjs-monorepo2.8k—~3.3kAutomated safety check: PassNone

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Works with

Questions about Nodejs Keccak256

What does Nodejs Keccak256 do?

JavaScriptとTypeScriptにおけるEthereumハッシュバグを防ぐ。NodeのSHA3-256はNIST SHA3であり、Ethereum Keccak-256ではなく、セレクター、署名、ストレージスロット、アドレス導出を静かに破壊する。. Nodejs Keccak256 is an agent skill from affaan-m/ECC.

How do I install Nodejs Keccak256 in Claude Code?

Run `npx skills add affaan-m/ECC --skill nodejs-keccak256 -a claude-code`. Or copy the skill folder (docs/ja-JP/skills/nodejs-keccak256 in affaan-m/ECC) into .claude/skills/nodejs-keccak256 in your project. Claude Code loads it when a task matches its description.

How do I install Nodejs Keccak256 in Codex?

Run `npx skills add affaan-m/ECC --skill nodejs-keccak256 -a codex`. Or copy the skill folder (docs/ja-JP/skills/nodejs-keccak256 in affaan-m/ECC) into .agents/skills/nodejs-keccak256 in your project. Codex loads it when a task matches its description.

Can I use Nodejs Keccak256 in Cursor, Gemini CLI or GitHub Copilot?

Cursor, Gemini CLI, GitHub Copilot and OpenCode also load SKILL.md folders. With the skills CLI, run `npx skills add affaan-m/ECC --skill nodejs-keccak256 -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/nodejs-keccak256, .gemini/skills/nodejs-keccak256, .github/skills/nodejs-keccak256 and .opencode/skills/nodejs-keccak256 in your project.

What does Nodejs Keccak256 need to run?

SKILL.md names no scripts, command-line tools or credentials: Nodejs Keccak256 is instructions for the agent only. Our summary lists: Node.js.

Does Nodejs Keccak256 access the network?

SKILL.md contains no URLs. Any network use would come from the scripts or tools the agent runs. This is read from the text; nothing was executed.

Is Nodejs Keccak256 safe to install?

Our automated static check of SKILL.md found no risky patterns, such as piping downloads into a shell, reading credential files or hidden Unicode. It is not a guarantee. Review the folder before installing.

What licence does Nodejs Keccak256 use?

Nodejs Keccak256 is published under the MIT licence (the repository's licence). It allows redistribution, so the full SKILL.md is shown on this page.

How many tokens does Nodejs Keccak256 use?

About 631 tokens (SKILL.md is roughly 2.5k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full.

What are the alternatives to Nodejs Keccak256?

Skills that share tags, products or a category with Nodejs Keccak256: Bun Development (GabrielMartinMoran/mind, 148 stars), Generate Release Notes (teambit/bit, 18k stars), Compromise NLP Library (spencermountain/compromise, 12k stars) and Release Round (ethereumjs/ethereumjs-monorepo, 2.8k stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.

Who maintains Nodejs Keccak256?

affaan-m (a GitHub user) maintains it in affaan-m/ECC, which has 275,546 GitHub stars. The repository holds 673 skills in this directory. The repository was last updated on October 5, 2026.

Source: affaan-m/ECC on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.