chromium/crypto/p224_spake.h

// Copyright 2012 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef CRYPTO_P224_SPAKE_H_
#define CRYPTO_P224_SPAKE_H_

#include <stdint.h>

#include <string>
#include <string_view>

#include "base/gtest_prod_util.h"
#include "crypto/sha2.h"

namespace crypto {

// P224EncryptedKeyExchange implements SPAKE2, a variant of Encrypted
// Key Exchange. It allows two parties that have a secret common
// password to establish a common secure key by exchanging messages
// over an insecure channel without disclosing the password.
//
// The password can be low entropy as authenticating with an attacker only
// gives the attacker a one-shot password oracle. No other information about
// the password is leaked. (However, you must be sure to limit the number of
// permitted authentication attempts otherwise they get many one-shot oracles.)
//
// The protocol requires several RTTs (actually two, but you shouldn't assume
// that.) To use the object, call GetNextMessage() and pass that message to the
// peer. Get a message from the peer and feed it into ProcessMessage. Then
// examine the return value of ProcessMessage:
//   kResultPending: Another round is required. Call GetNextMessage and repeat.
//   kResultFailed: The authentication has failed. You can get a human readable
//       error message by calling error().
//   kResultSuccess: The authentication was successful.
//
// In each exchange, each peer always sends a message.
class CRYPTO_EXPORT P224EncryptedKeyExchange { … };

}  // namespace crypto

#endif  // CRYPTO_P224_SPAKE_H_