code: protected PGPSecretKey findSecretKey(InputStream secretKey, final long keyId) throws IOException, PGPException {
      LOGGER.trace("findSecretKey(InputStream, long)");
      LOGGER.trace("Secret Key: {}, Key ID: {}", secretKey == null ? "not set" : "set", keyId);
      return findSecretKey(secretKey, new KeyFilter<PGPSecretKey>() {
        @Override
        public boolean accept(PGPSecretKey secretKey) {
          return secretKey.getKeyID() == keyId;
        }
      });
    }
docs: helper method to read a specific secret key
  
  @param secretKey
  the secret key stream
  @param keyId
  the key id
  @return the applicable secret key or null if none is part of the stream for the key id
  @throws IOException
  @throws PGPException