sphinxcrypto 0.1.1

// constants.rs - sphinx cryptographic packet format constants
// Copyright (C) 2018  David Anthony Stainton.
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program.  If not, see <http://www.gnu.org/licenses/>.

//! The Sphinx packet geometry is parameterization.

use super::internal_crypto::{GROUP_ELEMENT_SIZE, MAC_SIZE, SPRP_KEY_SIZE, SPRP_IV_SIZE, HASH_SIZE};
use super::commands::{RECIPIENT_SIZE, SURB_REPLY_SIZE};

/// The size in bytes of the Sphinx packet replay tags.
pub const SPHINX_REPLAY_TAG_SIZE: usize = HASH_SIZE;

/// The maximum number of hops a packet will traverse.
pub const MAX_HOPS: usize = 5;

/// The length of the usable forward payload
/// of a Sphinx packet in bytes.
pub const FORWARD_PAYLOAD_SIZE: usize = 50 * 1024;

/// The node identifier size in bytes.
pub const NODE_ID_SIZE: usize = 32;

/// The recipient identifier size in bytes.
pub const RECIPIENT_ID_SIZE: usize = 64;

/// The SURB identifier size in bytes.
pub const SURB_ID_SIZE: usize = 16;

/// The "authenticated data" portion of the Sphinx
/// packet header which as specified contains the
/// version number.
pub const AD_SIZE: usize = 2;

/// The first section of our Sphinx packet, the authenticated
/// unencrypted data containing version number.
pub const V0_AD: [u8; 2] = [0u8; 2];

/// The size in bytes of the payload tag.
pub const PAYLOAD_TAG_SIZE: usize = 16;

/// The size of a BlockSphinxPlaintext in bytes.
pub const SPHINX_PLAINTEXT_HEADER_SIZE: usize = 1 + 1;

/// The size of the user portion of the forward payload.
pub const USER_FORWARD_PAYLOAD_SIZE: usize = FORWARD_PAYLOAD_SIZE - (SPHINX_PLAINTEXT_HEADER_SIZE + SURB_SIZE);

/// The size of a Single Use Reply Block
pub const SURB_SIZE: usize = HEADER_SIZE + NODE_ID_SIZE + SPRP_KEY_SIZE + SPRP_IV_SIZE;

/// The size of the Sphinx packet header in bytes.
pub const HEADER_SIZE: usize = AD_SIZE + GROUP_ELEMENT_SIZE + ROUTING_INFO_SIZE + MAC_SIZE;

/// The Sphinx packet payload size in bytes.
pub const PAYLOAD_SIZE: usize = PAYLOAD_TAG_SIZE + FORWARD_PAYLOAD_SIZE;

/// The size in bytes of each routing info slot.
pub const PER_HOP_ROUTING_INFO_SIZE: usize = RECIPIENT_SIZE + SURB_REPLY_SIZE;

/// The size in bytes of the routing info section of the packet
/// header.
pub const ROUTING_INFO_SIZE: usize = PER_HOP_ROUTING_INFO_SIZE * MAX_HOPS;