Signature Algorithm Checker

Check the signature algorithm used by SSL certificates

About Signature Algorithm Checker

Certificate signature algorithms define how a certificate's content is cryptographically signed by the issuing CA. Modern certificates should use SHA-256 or stronger hash algorithms combined with RSA, ECDSA, or Ed25519 signatures. Our Signature Algorithm Checker retrieves the algorithm details and OID from a server's certificate and evaluates its cryptographic strength against current best practices.

How to Use

1Enter the domain name whose certificate signature algorithm you want to check.
2Click "Check" to retrieve and analyze the signature algorithm details.
3Review the algorithm name, OID, strength rating, and security recommendation.

Use Cases

•Verify that certificates use SHA-256 or stronger signature algorithms
•Identify certificates still using deprecated SHA-1 signatures
•Audit certificate chains for consistent signature algorithm strength
•Ensure compliance with CA/B Forum and browser vendor requirements

Frequently Asked Questions

SHA-256 with RSA (sha256WithRSAEncryption) or SHA-256 with ECDSA (ecdsa-with-SHA256) are the minimum standards. Ed25519 signatures are also excellent. Avoid SHA-1 based algorithms entirely.

SHA-1 is vulnerable to collision attacks — researchers demonstrated a practical SHA-1 collision in 2017. All major browsers now reject SHA-1-signed certificates and mark them as insecure.

The Object Identifier (OID) uniquely identifies the signature algorithm in the certificate. For example, 1.2.840.113549.1.1.11 represents sha256WithRSAEncryption. Each algorithm has a distinct OID defined by standards bodies.

Tips & Best Practices

•Use strong signature algorithms (SHA-256, SHA-384, SHA-512)
•Verify signature algorithm meets your security requirements
•Avoid weak algorithms (MD5, SHA-1) for certificate signatures
•Monitor signature algorithm usage across your certificate infrastructure

Technical Details

Algorithm: Certificate signature algorithm identification and analysis
Security: Algorithm security assessment and recommendations
Standards: NIST and CA/Browser Forum algorithm requirements
Output: Signature algorithm details with security assessment