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// Copyright 2015 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
// Definitions related to the SecureMessage format, used by CryptAuth. Do not
// edit unless transcribing from server definitions.
syntax = "proto2";
package securemessage;
option optimize_for = LITE_RUNTIME;
message SecureMessage {
// Must contain a HeaderAndBody message.
required bytes header_and_body = 1;
// Signature of header_and_body.
required bytes signature = 2;
}
// Supported "signature" schemes (both symmetric key and public key based).
enum SigScheme {
HMAC_SHA256 = 1;
ECDSA_P256_SHA256 = 2;
// Not recommended -- use ECDSA_P256_SHA256 instead
RSA2048_SHA256 = 3;
}
// Supported encryption schemes.
enum EncScheme {
// No encryption.
NONE = 1;
AES_256_CBC = 2;
}
message Header {
required SigScheme signature_scheme = 1;
required EncScheme encryption_scheme = 2;
// Identifies the verification key.
optional bytes verification_key_id = 3;
// Identifies the decryption key.
optional bytes decryption_key_id = 4;
// Encryption may use an IV.
optional bytes iv = 5;
// Arbitrary per-protocol public data, to be sent with the plain-text header.
optional bytes public_metadata = 6;
// The length of some associated data that is not sent in this SecureMessage,
// but which will be bound to the signature.
optional uint32 associated_data_length = 7 [default = 0];
}
message HeaderAndBody {
// Public data about this message (to be bound in the signature).
required Header header = 1;
// Payload data.
required bytes body = 2;
}
// A list of supported public key types.
enum PublicKeyType {
EC_P256 = 1;
RSA2048 = 2;
// 2048-bit MODP group 14, from RFC 3526.
DH2048_MODP = 3;
}
// A convenience proto for encoding NIST P-256 elliptic curve public keys.
message EcP256PublicKey {
// x and y are encoded in big-endian two's complement (slightly wasteful)
// Client MUST verify (x,y) is a valid point on NIST P256.
required bytes x = 1;
required bytes y = 2;
}
// A convenience proto for encoding RSA public keys with small exponents.
message SimpleRsaPublicKey {
// Encoded in big-endian two's complement.
required bytes n = 1;
optional int32 e = 2 [default = 65537];
}
// A convenience proto for encoding Diffie-Hellman public keys,
// for use only when Elliptic Curve based key exchanges are not possible.
// (Note that the group parameters must be specified separately).
message DhPublicKey {
// Big-endian two's complement encoded group element.
required bytes y = 1;
}
message GenericPublicKey {
required PublicKeyType type = 1;
optional EcP256PublicKey ec_p256_public_key = 2;
optional SimpleRsaPublicKey rsa2048_public_key = 3;
// Use only as a last resort.
optional DhPublicKey dh2048_public_key = 4;
}
// Used by protocols for communicating between a pair of devices.
message DeviceToDeviceMessage {
// The payload of the message.
optional bytes message = 1;
// The sequence number of the message - must be increasing.
optional int32 sequence_number = 2;
}
// Sent as the first message from initiator to responder in an unauthenticated
// Diffie-Hellman Key Exchange.
message InitiatorHello {
optional GenericPublicKey public_dh_key = 1;
}
// Sent inside the header of the first message from the responder to the
// initiator in an unauthenticated Diffie-Hellman Key Exchange.
message ResponderHello {
optional GenericPublicKey public_dh_key = 1;
}
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