@Override
  public boolean equalsKey(Key o) {
    if (!(o instanceof AesCtrHmacAeadKey)) {
      return false;
    }
    AesCtrHmacAeadKey that = (AesCtrHmacAeadKey) o;
    // Since outputPrefix is a function of parameters, we can ignore it here.
    return that.parameters.equals(parameters)
        && that.aesKeyBytes.equalsSecretBytes(aesKeyBytes)
        && that.hmacKeyBytes.equalsSecretBytes(hmacKeyBytes)
        && Objects.equals(that.idRequirement, idRequirement);
  }
Returns the underlying HMAC key bytes.
java_src/src/main/java/com/google/crypto/tink/aead/AesCtrHmacAeadKey.java