ZeroTierOne/node/Poly1305.hpp

/*
 * Copyright (c)2019 ZeroTier, Inc.
 *
 * Use of this software is governed by the Business Source License included
 * in the LICENSE.TXT file in the project's root directory.
 *
 * Change Date: 2026-01-01
 *
 * On the date above, in accordance with the Business Source License, use
 * of this software will be governed by version 2.0 of the Apache License.
 */
/****/

#ifndef ZT_POLY1305_HPP
#define ZT_POLY1305_HPP

namespace ZeroTier {

#define ZT_POLY1305_KEY_LEN 32
#define ZT_POLY1305_MAC_LEN 16

/**
 * Poly1305 one-time authentication code
 *
 * This takes a one-time-use 32-byte key and generates a 16-byte message
 * authentication code. The key must never be re-used for a different
 * message.
 *
 * In Packet this is done by using the first 32 bytes of the stream cipher
 * keystream as a one-time-use key. These 32 bytes are then discarded and
 * the packet is encrypted with the next N bytes.
 */
class Poly1305 {
  public:
    /**
     * Compute a one-time authentication code
     *
     * @param auth Buffer to receive code -- MUST be 16 bytes in length
     * @param data Data to authenticate
     * @param len Length of data to authenticate in bytes
     * @param key 32-byte one-time use key to authenticate data (must not be reused)
     */
    static void compute(void* auth, const void* data, unsigned int len, const void* key);
};

}   // namespace ZeroTier

#endif