SSH Public Key Fingerprint Generator

What does the SSH Public Key Fingerprint Generator do?

The SSH Public Key Fingerprint Generator & Type Inspector parses OpenSSH public keys (such as ssh-ed25519, ssh-rsa, ecdsa-sha2-nistp256, and ssh-dss) and computes SHA256 (used by GitHub/OpenSSH) and MD5 (used by AWS EC2 Key Pairs) cryptographic fingerprints. It extracts key bit lengths, comments/emails, and renders visual ASCII drunken bishop randomart.

Core Concepts

Understanding SSH public key fingerprints and inspection:

• Binary Key Parsing: Decodes the Base64 binary payload to determine key algorithm, public exponent, modulus bit length, and elliptic curve parameters.
• SHA256 & MD5 Fingerprints: Computes standard unpadded Base64 SHA256 hashes (SHA256:...) and colon-delimited MD5 hex digests (MD5:xx:xx:...).
• OpenSSH Randomart Visualizer: Implements the official OpenSSH drunken bishop random walk algorithm on a 9x17 character matrix.

How to use the tool?

1. Paste OpenSSH Public Key: Paste your public key string (e.g. from ~/.ssh/id_ed25519.pub) or click Load Sample Key.
2. Generate Fingerprints: Click Generate SSH Fingerprint to calculate hashes and inspect key parameters.
3. Copy Fingerprints or Art: Click Copy next to the SHA256 fingerprint, MD5 digest, or visual randomart.

Related Developer Utilities

If you work with SSH keys, authentication, and cryptographic fingerprints, explore these complementary tools:

• SSH Public Key Format Converter: Convert keys between OpenSSH, RFC 4716, and PEM formats.
• SSH Config to Ansible Inventory Converter: Convert ~/.ssh/config to Ansible inventories.
• SSH Config to /etc/hosts Converter: Convert SSH config hosts into /etc/hosts aliases.
• AWS IAM OIDC Thumbprint Calculator: Calculate 40-character SHA-1 CA thumbprints for GitHub Actions.

REST API Integration

Blueutils provides a free REST API endpoint (POST https://blueutils.com/api/ssh/ssh-key-fingerprint) to programmatically calculate SHA256 (GitHub/OpenSSH) and MD5 (AWS EC2) fingerprints, parse key algorithms, bit strength, and generate randomart visual graphs.

API Request Parameters

API Request Payload Examples

cURL

curl -X POST https://blueutils.com/api/ssh/ssh-key-fingerprint \
  -H "Content-Type: application/json" \
  -d '{
    "rawText": "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIGt7X2N+h4l7T5rL6H3n8P9Z1m+2q4w6e8r0t2y4u6i8 developer@workstation"
  }'

Python

import requests

url = "https://blueutils.com/api/ssh/ssh-key-fingerprint"
payload = {
    "rawText": "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIGt7X2N+h4l7T5rL6H3n8P9Z1m+2q4w6e8r0t2y4u6i8 developer@workstation"
}
headers = {"Content-Type": "application/json"}
response = requests.post(url, json=payload, headers=headers)
print(response.json())

Java

import java.net.URI;
import java.net.http.HttpClient;
import java.net.http.HttpRequest;
import java.net.http.HttpResponse;

public class Main {
    public static void main(String[] args) throws Exception {
        String jsonPayload = """
            {
                "rawText": "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIGt7X2N+h4l7T5rL6H3n8P9Z1m+2q4w6e8r0t2y4u6i8 developer@workstation"
            }
            """;

        HttpClient client = HttpClient.newHttpClient();
        HttpRequest request = HttpRequest.newBuilder()
            .uri(URI.create("https://blueutils.com/api/ssh/ssh-key-fingerprint"))
            .header("Content-Type", "application/json")
            .POST(HttpRequest.BodyPublishers.ofString(jsonPayload))
            .build();

        HttpResponse<String> response = client.send(request, HttpResponse.BodyHandlers.ofString());
        System.out.println(response.body());
    }
}

API Response Parameters

API Response Payload Examples

Success Response (HTTP 200 OK)

{
  "isValid": true,
  "algorithm": "ssh-ed25519",
  "bitLength": 256,
  "comment": "developer@workstation",
  "sha256Fingerprint": "SHA256:4t7X7k9M+3w2kL...",
  "md5Fingerprint": "MD5:a1:b2:c3:d4:e5:f6:07:18:29:3a:4b:5c:6d:7e:8f:90",
  "randomart": "+--[ED25519 256]--+\n|  ..+.           |\n| . o o.          |\n|  + + o          |\n+-----------------+"
}

Validation Failure Response (HTTP 400 Bad Request)

{
  "isValid": false,
  "error": "Invalid SSH public key: Expected at least 2 tokens (key type and Base64 encoded key payload)."
}

Rate Limit Exceeded Response (HTTP 429 Too Many Requests)

{
  "error": "API rate limit exceeded. Please wait or contact support@blueutils.com."
}

Why use an API to calculate SSH key fingerprints?

Integrating the SSH Key Fingerprint API into cloud provisioning scripts, GitHub Actions workflows, or AI agent tool calling provides key benefits:

• Rapid Script Validation: Verifies that deployed SSH public keys match AWS EC2 Key Pairs or GitHub deploy keys without executing shell binaries.
• Optimized Token Efficiency for AI Agents: LLMs cannot reliably compute binary SHA256 or MD5 hashes from Base64 key blobs. Calling the API extracts fingerprints deterministically without token consumption.
• Deterministic Accuracy Without Hallucinations: Ensures 100% byte-accurate OpenSSH and AWS EC2 fingerprint formats.

Native Usage

How to generate SSH key fingerprints locally in terminal environments or scripts:

Windows (CMD / PowerShell)

:: Generate SHA256 and MD5 fingerprints from local key file in Windows
ssh-keygen -l -f %USERPROFILE%\.ssh\id_ed25519.pub
ssh-keygen -l -E md5 -f %USERPROFILE%\.ssh\id_ed25519.pub

Linux / Unix (Bash)

# SHA256 Fingerprint in Linux
ssh-keygen -l -f ~/.ssh/id_rsa.pub

# MD5 Fingerprint in Linux (AWS EC2 format)
ssh-keygen -l -E md5 -f ~/.ssh/id_rsa.pub

Python

Using Python:

import base64
import hashlib

def get_ssh_fingerprints(pubkey_str):
    parts = pubkey_str.strip().split()
    key_bytes = base64.b64decode(parts[1])
    sha256 = "SHA256:" + base64.b64encode(hashlib.sha256(key_bytes).digest()).decode('utf-8').rstrip('=')
    md5 = "MD5:" + ":".join(f"{b:02x}" for b in hashlib.md5(key_bytes).digest())
    return sha256, md5

print(get_ssh_fingerprints("ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIGt7X2N+h4l7T5rL6H3n8P9Z1m+2q4w6e8r0t2y4u6i8 user@host"))

Java

Using Java:

import java.security.MessageDigest;
import java.util.Base64;

public class SshFingerprintExample {
    public static void main(String[] args) throws Exception {
        String keyB64 = "AAAAC3NzaC1lZDI1NTE5AAAAIGt7X2N+h4l7T5rL6H3n8P9Z1m+2q4w6e8r0t2y4u6i8";
        byte[] keyBytes = Base64.getDecoder().decode(keyB64);
        byte[] digest = MessageDigest.getInstance("SHA-256").digest(keyBytes);
        String fp = "SHA256:" + Base64.getEncoder().withoutPadding().encodeToString(digest);
        System.out.println(fp);
    }
}