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// Copyright 2016 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
syntax = "proto3";
package cobalt;
option go_package = "cobalt";
// NOTE: This copy of encrypted_message.proto is used by the Cobalt client.
// A second copy of this file is used by the Cobalt Shuffler and Analyzer
// running in Google production. It is necessary to have two copies due to
// requirements by the Google Logs Privacy team regarding the location of
// of .proto files used in logs processing pipelines. Any changes to this
// file must be replicated in the other copy of the file.
// An EncryptedMessage carries the encrypted bytes of another proto message,
// along with information about how it is encrypted.
// Observations collected via Cobalt are doubly encrypted. First each individual
// message is encrypted to the Analyzer that will process it. Second each
// Envelope containing many observations is encrypted to the Shuffler. We use
// the EncryptedMessage proto to carry the ciphertext in both cases.
message EncryptedMessage {
// The different schemes used in Cobalt to encrypt a message.
enum EncryptionScheme {
// The message is not encrypted. |ciphertext| contains plaintext bytes of a
// serialized protocol buffer message. This scheme must only be used in
// tests.
NONE = 0;
// Hybrid Cipher using elliptic curve Diffie-Hellman, version 1.
// Hybrid cipher compatible with Tink hybrid encryption/decryption
// primitives declared in
// third_party/tink/cc/hybrid/hybrid_key_templates.h
// Multiple hybrid encryption schemes are supported and indicated by the
// type of key used.
// Which scheme was used to encrypt this message?
EncryptionScheme scheme = 1;
// 32-byte fingerprint (SHA256) of the recipient’s public key.
// This is used to facilitate key rotation.
bytes public_key_fingerprint = 2;
// The |ciphertext| field contains the bytes of the encryption of the standard
// serialization of one of the following types of proto messages:
// - A cobalt.Envelope, as defined in envelope.proto.
// EncryptedMessages containing Envelopes are the input to the Shuffler.
// - A cobalt.Observation2, as defined in observation2.proto.
// An ObservationBatch (defined in observation_batch.proto) contains
// EncryptedMessages of this type. ObservationBatches are output from the
// Shuffler.
bytes ciphertext = 3;