Use custom certificates for SSL/TLS on Android. From https://github.com/square/okhttp/issues/173 and https://plus.google.com/+JakeWharton/posts/go9jBhHw3TY

goodSslSocketFactory.java

SSLSocketFactory goodSslSocketFactory(Context context) {
        KeyStore trusted = KeyStore.getInstance("BKS");
        InputStream in = context.getResources().openRawResource(R.raw.truststore);
        trusted.load(in, TRUST_STORE_PASSWORD);
        SSLContext sslContext = SSLContext.getInstance("TLS");
        TrustManagerFactory trustManagerFactory = TrustManagerFactory.getInstance(
                        TrustManagerFactory.getDefaultAlgorithm());
        trustManagerFactory.init(trusted);
        sslContext.init(null, trustManagerFactory.getTrustManagers(), null);
        return sslContext.getSocketFactory();
}