static String getKeyType() {
    return "type.googleapis.com/google.crypto.tink.RsaSsaPkcs1PrivateKey";
  }
This key manager generates new {@code RsaSsaPkcs1PrivateKey} keys and produces new instances of
{@code RsaSsaPkcs1SignJce}.
java_src/src/main/java/com/google/crypto/tink/signature/RsaSsaPkcs1SignKeyManager.java