SSH Private Key (OpenSSH Format) Regex for Java

What this pattern does

This page provides a comprehensive, battle-tested regular expression for matching ssh private key (openssh format), ported and verified for Java. In security-sensitive code, using an unverified regex can open the door to both false positives and denial-of-service attacks. The snippet below is ready to drop into your Java project — whether you're validating in a Spring Boot controller, a Jakarta EE service, or a standalone utility class.

Java Implementation

// SSH Private Key (OpenSSH Format)
// ReDoS-safe | RegexVault — Security > Certificates & PKI

import java.util.regex.Pattern;

public class SshPrivateKeyOpensshFormatValidator {
    private static final Pattern PATTERN =
        Pattern.compile("-----BEGIN OPENSSH PRIVATE KEY-----[\\r\\n]+(?:[A-Za-z0-9+/=\\r\\n]{1,80}[\\r\\n]+)*-----END OPENSSH PRIVATE KEY-----");

    public static boolean validate(String input) {
        return PATTERN.matcher(input).matches();
    }

    // Example
    public static void main(String[] args) {
        System.out.println(validate("-----BEGIN OPENSSH PRIVATE KEY-----
b3BlbnNzaC1rZXktdjEAAAAAAAAA
-----END OPENSSH PRIVATE KEY-----")); // true
    }
}

Test Cases

When to use this pattern

This pattern is drawn from the Security > Certificates & PKI category and carries a ReDoS-safe certification. That matters for Java developers because critical in Java applications since the JVM regex engine uses backtracking and is susceptible to ReDoS without careful pattern design. RegexVault audits patterns against known backtracking attack vectors, ensuring you have the necessary context before using this regex in a high-stakes production environment.

Common Pitfalls

Technical Notes

OpenSSH private key format (openssh-key-v1) is the default since OpenSSH 6.5 (2014). Unlike PEM RSA keys, this format includes key type metadata and may be passphrase-protected. The base64 payload includes the key type, public key, and encrypted private key.