Cipher Suite Selection and Configuration

Cipher Suite Selection and Configuration

Cipher suite selection balances security, performance, and compatibility. Modern cipher suites provide strong security with minimal performance impact, but legacy client support might require carefully chosen compromises. Understanding cipher suite components helps make informed decisions about API security configuration.

// Java example of TLS configuration with specific cipher suites
import javax.net.ssl.*;
import java.security.KeyStore;
import java.io.FileInputStream;

public class SecureAPIServer {
    public static SSLContext createSSLContext() throws Exception {
        // Load keystore
        KeyStore keyStore = KeyStore.getInstance("JKS");
        keyStore.load(new FileInputStream("api-keystore.jks"), "password".toCharArray());
        
        // Initialize key manager
        KeyManagerFactory kmf = KeyManagerFactory.getInstance("SunX509");
        kmf.init(keyStore, "password".toCharArray());
        
        // Create SSL context
        SSLContext sslContext = SSLContext.getInstance("TLS");
        sslContext.init(kmf.getKeyManagers(), null, null);
        
        return sslContext;
    }
    
    public static void configureSSLEngine(SSLEngine engine) {
        // Enable only TLS 1.2 and 1.3
        engine.setEnabledProtocols(new String[] {"TLSv1.2", "TLSv1.3"});
        
        // Configure cipher suites
        String[] cipherSuites = {
            // TLS 1.3 cipher suites
            "TLS_AES_128_GCM_SHA256",
            "TLS_AES_256_GCM_SHA384",
            "TLS_CHACHA20_POLY1305_SHA256",
            
            // TLS 1.2 cipher suites with forward secrecy
            "TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256",
            "TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384",
            "TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305_SHA256"
        };
        
        engine.setEnabledCipherSuites(cipherSuites);
        engine.setUseClientMode(false);
        engine.setNeedClientAuth(false); // Set to true for mutual TLS
    }
}

Forward secrecy protects past communications even if server private keys are compromised. Prioritize ECDHE and DHE cipher suites that provide forward secrecy. Remove static RSA key exchange cipher suites. Configure appropriate DH parameter sizes (2048 bits minimum) for DHE suites. Monitor for weak DH parameter vulnerabilities like Logjam.

Performance considerations influence cipher suite selection for high-volume APIs. AES-GCM provides excellent performance on modern hardware with AES-NI support. ChaCha20-Poly1305 offers better performance on mobile devices without hardware acceleration. Benchmark different cipher suites with your actual API workload to optimize selection.