@Override
  public byte[] encrypt(final byte[] plaintext, final byte[] associatedData)
      throws GeneralSecurityException {
    try {
      Map<String, Object> content = new HashMap<>();
      content.put("plaintext", Base64.getEncoder().encodeToString(plaintext));
      content.put("context", Base64.getEncoder().encodeToString(associatedData));
      LogicalResponse resp = vaultApi.write(encPath, content);
      handleResponse(resp);
      return resp.getData().get("ciphertext").getBytes();
    } catch (VaultException e) {
      throw new GeneralSecurityException("encryption failed", e);
    }
  }
A {@link Aead} that forwards encryption/decryption requests to a key in <a
href="https://www.vaultproject.io/">Hashicorp Vault</a>.
java_src/src/main/java/com/google/crypto/tink/integration/hcvault/HcVaultAead.java