SSH Public Key Fingerprint & Converter
SSH Public Key Fingerprint & Converter: Decodes Base64 key body, computes SHA-256 hash, and formats standard OpenSSH fingerprint.
About this ssh public key fingerprint & converter
SSH Public Key Fingerprint & Converter — browser-based utility.
How this tool works
Implements client-side SSH Public Key Fingerprint & Converter operations. Decodes Base64 key body, computes SHA-256 hash, and formats standard OpenSSH fingerprint specifically designed for a developer calculates the sha-256 fingerprint of an ssh public key before adding it to github.
- PEM Armor Stripping & DER Decoding: Strips '-----BEGIN CERTIFICATE-----' headers and decodes Base64 to raw ASN.1 DER binary bytes.
- ASN.1 Structure Traversal: Parses the TBSCertificate sequence, extracting serial numbers, signature algorithms, and X.500 distinguished names.
- Extension Extraction: Decodes X.509v3 extensions, extracting SAN DNS names, basic constraints (CA flag), and key usage flags.
- Diagnostic Reporting: Computes SHA-256 fingerprint, checks expiration status against the current date, and warns if certificates are expired or self-signed.
Worked example
Scenario: A developer calculates the SHA-256 fingerprint of an SSH public key before adding it to GitHub.
Sample input:
Processing: Decodes Base64 key body, computes SHA-256 hash, and formats standard OpenSSH fingerprint.
Illustrative output:
Limits and verification
Rejects corrupted PEM files with invalid Base64 characters or missing encapsulation boundaries. Warns users when inspecting self-signed root certificates or certificates with weak 1024-bit RSA keys.
Examples demonstrate an expected workflow; they do not prove every input or every branch of an external specification. Check important results with an independent source before using them for money, security, compliance, safety, or irreversible file changes.
Browser processing boundary
Tool input is processed by code running in the browser and is not intentionally sent to a CZOA processing API. The page can still request ordinary site assets, analytics, or advertising when those services are enabled. Browser extensions and managed-device software remain outside this tool's control.
Relevant references
These references govern or help explain the format, protocol, or calculation used here. Listing a reference does not claim certification or complete implementation of every optional feature.
Content owner: CZOA Tools · Last reviewed: 2026-09-15 · Review methodology
How to use it
- Enter, paste, or select your input data into the SSH Public Key Fingerprint & Converter workspace controls.
- Review available parameter fields, units, formats, or options configured for your task.
- Click the action button or observe immediate live calculations rendered in your browser runtime.
- Inspect the resulting output and any diagnostic messages, then copy or download the result if needed.
Frequently asked questions
Which SSH public keys can the fingerprint tool read?+
It accepts OpenSSH public-key text beginning with ssh-rsa, ssh-ed25519, ssh-dss, or ecdsa-sha2-, decodes the base64 blob, and validates that blob against the declared key format.
What did the browser fixture verify?+
A valid ssh-ed25519 sample with comment demo@czoa returned SHA256 fingerprint data, format ssh-ed25519, the comment, and 51 blob bytes.
How is the fingerprint formatted?+
It computes SHA-256 over the decoded public-key blob and returns OpenSSH-style SHA256 followed by base64 digest text with trailing padding removed.
Does a matching fingerprint prove the key owner?+
No. It identifies a public-key blob for comparison. Ownership, authorization, key revocation, server trust, and private-key possession are separate matters.