public static KeyTemplate createAesSivKeyTemplate(int keySize) {
    AesSivKeyFormat format = AesSivKeyFormat.newBuilder().setKeySize(keySize).build();
    return KeyTemplate.newBuilder()
        .setValue(format.toByteString())
        .setTypeUrl(AesSivKeyManager.getKeyType())
        .setOutputPrefixType(OutputPrefixType.TINK)
        .build();
  }
@return a {@code KeyTemplate} containing a {@code AesSivKeyFormat} with some specified
    parameters.
java_src/src/main/java/com/google/crypto/tink/daead/DeterministicAeadKeyTemplates.java