90 lines
3.8 KiB
Protocol Buffer
90 lines
3.8 KiB
Protocol Buffer
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// Copyright 2023 Google LLC
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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syntax = "proto3";
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package cobalt;
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option java_multiple_files = true;
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option java_package = "com.google.cobalt";
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////////////////////////////////////////////////////////////////////////////////
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// NOTE: This file is used by the Cobalt client and the Cobalt servers.
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// The source-of-truth of this file is located in Google's internsl code
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// repository, and the file is copied to Android where it is used by the Cobalt
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// client. Do not edit the copy of this file in this Android repo as those edits
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// will be overwritten when the file is next copied.
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////////////////////////////////////////////////////////////////////////////////
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// An EncryptedMessage carries the encrypted bytes of another proto message,
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// along with information about how it is encrypted.
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//
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// Observations collected via Cobalt are doubly encrypted. First each individual
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// message is encrypted to the Analyzer that will process it. Second each
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// Envelope containing many observations is encrypted to the Shuffler. We use
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// the EncryptedMessage proto to carry the ciphertext in both cases.
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//
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message EncryptedMessage {
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// The different schemes used in Cobalt to encrypt a message.
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enum EncryptionScheme {
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// The message is not encrypted. |ciphertext| contains plaintext bytes of a
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// serialized protocol buffer message. This scheme must only be used in
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// tests.
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NONE = 0;
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// Hybrid Cipher using elliptic curve Diffie-Hellman, version 1.
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HYBRID_ECDH_V1 = 1;
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// Hybrid cipher compatible with Tink hybrid encryption/decryption
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// primitives declared in
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// third_party/tink/cc/hybrid/hybrid_key_templates.h
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// Multiple hybrid encryption schemes are supported and indicated by the
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// type of key used.
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HYBRID_TINK = 2;
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}
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// Which scheme was used to encrypt this message?
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EncryptionScheme scheme = 1;
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// Which key was used to encrypt this message?
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// This key is mutually exclusive with |scheme| being set.
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uint32 key_index = 4;
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// 32-byte fingerprint (SHA256) of the recipient’s public key.
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// This is used to facilitate key rotation.
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bytes public_key_fingerprint = 2;
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// The |contribution_id| field is a cryptographically-secure random number
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// generated and attached by the Cobalt client. The shuffler counts the
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// number of unique ids to determine the contribution count per report.
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//
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// This field should only be set when the |ciphertext| contains a
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// cobalt.Observation that should be counted towards the shuffler threshold.
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// All other encrypted messages should not receive a |contribution_id|.
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//
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// Once an observation is encrypted and assigned a |contribution_id| it
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// should never be given another id or stored unencrypted.
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bytes contribution_id = 5;
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// The |ciphertext| field contains the bytes of the encryption of the standard
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// serialization of one of the following types of proto messages:
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//
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// - A cobalt.Envelope, as defined in Cobalt's envelope.proto.
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// EncryptedMessages containing Envelopes are the input to the Shuffler.
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//
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// - A cobalt.Observation, as defined in Cobalt's observation.proto.
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// An ObservationBatch (defined in observation_batch.proto) contains
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// EncryptedMessages of this type. ObservationBatches are output from the
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// Shuffler.
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bytes ciphertext = 3;
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}
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