private static KeyTemplate createHkdfKeyTemplate() {
    HkdfPrfKeyFormat format =
        HkdfPrfKeyFormat.newBuilder()
            .setKeySize(32) // the size in bytes of the HKDF key
            .setParams(HkdfPrfParams.newBuilder().setHash(HashType.SHA256))
            .build();
    return KeyTemplate.newBuilder()
        .setValue(format.toByteString())
        .setTypeUrl(HkdfPrfKeyManager.staticKeyType())
        .setOutputPrefixType(OutputPrefixType.RAW)
        .build();
  }
Key templates for PRF-Keys.

<p>We recommend to avoid this class in order to keep dependencies small.

<ul>
  <li>Using this class adds a dependency on protobuf. We hope that eventually it is possible to
      use Tink without a dependency on protobuf.
  <li>Using this class adds a dependency on classes for all involved key types.
</ul>

These dependencies all come from static class member variables, which are initialized when the
class is loaded. This implies that static analysis and code minimization tools (such as proguard)
cannot remove the usages either.

<p>Instead, we recommend to use {@code KeysetHandle.generateEntryFromParametersName} or {@code
KeysetHandle.generateEntryFromParameters}.

@deprecated Use PredefinedPrfParameters instead.
java_src/src/main/java/com/google/crypto/tink/prf/PrfKeyTemplates.java