e194. listing all available cryptographic services.txt

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The providers of cryptographic services such as key generation algorithms, register their services with the Security class. A service is represented by a name of the form: 
    
service-type.service-implementation


An example of a service entry is SecureRandom.SHA1PRNG. 
    // This method returns all available services types
    public static String[] getServiceTypes() {
        Set result = new HashSet();
    
        // All all providers
        Provider[] providers = Security.getProviders();
        for (int i=0; i<providers.length; i++) {
            // Get services provided by each provider
            Set keys = providers[i].keySet();
            for (Iterator it=keys.iterator(); it.hasNext(); ) {
                String key = (String)it.next();
                key = key.split(" ")[0];
    
                if (key.startsWith("Alg.Alias.")) {
                    // Strip the alias
                    key = key.substring(10);
                }
                int ix = key.indexOf('.');
                result.add(key.substring(0, ix));
            }
        }
        return (String[])result.toArray(new String[result.size()]);
    }
    
    // This method returns the available implementations for a service type
    public static String[] getCryptoImpls(String serviceType) {
        Set result = new HashSet();
    
        // All all providers
        Provider[] providers = Security.getProviders();
        for (int i=0; i<providers.length; i++) {
            // Get services provided by each provider
            Set keys = providers[i].keySet();
            for (Iterator it=keys.iterator(); it.hasNext(); ) {
                String key = (String)it.next();
                key = key.split(" ")[0];
    
                if (key.startsWith(serviceType+".")) {
                    result.add(key.substring(serviceType.length()+1));
                } else if (key.startsWith("Alg.Alias."+serviceType+".")) {
                    // This is an alias
                    result.add(key.substring(serviceType.length()+11));
                }
            }
        }
        return (String[])result.toArray(new String[result.size()]);
    }

Here's a sample list of service types: 
    AlgorithmParameterGenerator
    AlgorithmParameters
    CertPathBuilder
    CertPathValidator
    CertStore
    CertificateFactory
    Cipher
    GssApiMechanism
    KeyAgreement
    KeyFactory
    KeyGenerator
    KeyManagerFactory
    KeyPairGenerator
    KeyStore
    Mac
    MessageDigest
    SSLContext
    SecretKeyFactory
    SecureRandom
    Signature
    TrustManagerFactory

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