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SSH Key Generator (Ed25519 / ECDSA / RSA)

開発者

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入力

出力

クライアント側

秘密鍵

公開鍵

Key Fingerprint

Quick Setup Guide

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ガイド

SSH Key Generator

Generate SSH key pairs directly in your browser using the Web Crypto API. Supports Ed25519 (recommended), ECDSA P-256/P-384, and RSA 2048/4096. Your private key is generated locally and never leaves your browser. Download keys in OpenSSH format, view fingerprints, and get quick setup commands.

使い方

Select your preferred algorithm (Ed25519 is recommended for most use cases), optionally add a comment and passphrase, then click Generate. The tool creates a public/private key pair displayed in OpenSSH format. Copy or download both keys, check the SHA-256 and MD5 fingerprints, and follow the quick setup guide to install your keys on a server.

特徴

5 Algorithm Options — Ed25519 (modern, fast, recommended), ECDSA P-256, ECDSA P-384, RSA 2048, and RSA 4096 (legacy compatibility).
OpenSSH Format Output — Private and public keys in standard OpenSSH format, ready to use with ssh, scp, and ssh-agent.
Key Fingerprints — SHA-256 and MD5 fingerprints displayed for verification, matching the output of ssh-keygen -l.
Download & Copy — Download private key (id_ed25519 / id_ecdsa / id_rsa) and public key (.pub) files, or copy to clipboard.
Custom Comment — Set the comment field appended to the public key (typically user@hostname).
Quick Setup Guide — Copyable SSH commands customized to your selected algorithm: set permissions, add to authorized_keys, add to agent, and connect.
Browser-Only Security — Uses the Web Crypto API (SubtleCrypto). Your private key is generated in your browser’s cryptographic engine and never transmitted anywhere.
Security Guidance — Prominent notice about key handling best practices and when to use local ssh-keygen instead.

Supported Algorithms

Ed25519 (Recommended): Modern elliptic curve algorithm. Fast, secure, small key size (256 bits). Supported by OpenSSH 6.5+ and all modern SSH clients. Best choice for new deployments.
ECDSA P-256 / P-384: Elliptic curve with NIST standard curves. Good performance and security. Widely supported.
RSA 2048: Classic algorithm. Universal compatibility but larger keys. Minimum recommended size for new keys.
RSA 4096: Maximum strength RSA. Use when interacting with legacy systems that don’t support Ed25519 or ECDSA.

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Is it safe to generate SSH keys in a browser?

This tool uses the Web Crypto API (SubtleCrypto), which is the browser’s built-in cryptographic engine — the same technology that secures HTTPS connections. Your private key is generated locally in your browser and never sent to any server. However, for production servers and high-security environments, generating keys locally with ssh-keygen is considered best practice because it eliminates any browser-related attack surface. This tool is ideal for development, testing, quick setups, and situations where you don’t have terminal access.

Which SSH key algorithm should I choose?

Ed25519 is recommended for almost all use cases. It’s modern, fast, produces small keys (68 characters for the public key vs 400+ for RSA), and is considered highly secure. Use RSA 4096 only if you need compatibility with very old SSH servers (pre-2014) or systems that explicitly require RSA. ECDSA is a middle ground — good security and performance with NIST-standard curves. If in doubt, choose Ed25519.

What is an SSH key fingerprint?

A fingerprint is a short hash of your public key used for verification. When you connect to a server for the first time, SSH shows the server’s key fingerprint so you can verify you’re connecting to the right host. Similarly, your key’s fingerprint helps administrators verify which key you’re using. SHA-256 fingerprints (e.g., SHA256:abcdef…) are the modern standard. MD5 fingerprints (e.g., ab:cd:ef:…) are legacy but still used by some older tools.

How do I add my SSH key to a server?

After generating your key pair: 1) Save the private key to ~/.ssh/ (e.g., ~/.ssh/id_ed25519). 2) Set permissions: chmod 600 ~/.ssh/id_ed25519. 3) Copy the public key to the server’s ~/.ssh/authorized_keys file — either manually or with ssh-copy-id. 4) Test the connection: ssh -i ~/.ssh/id_ed25519 user@server. For GitHub/GitLab, paste the public key in your account’s SSH key settings. The quick setup guide in this tool provides copyable commands for each step.

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