tiny.reticulum.wire.proof

1const std = @import("std");23/// 32 bytes, the width of the packet hash a proof (the signed reply that tells4/// a sender its packet arrived) signs, for sizing the hash, following5/// Reticulum@1.5.0 RNS/Packet.py:403.6pub const packet_hash_bytes: u16 = 32;7/// 64 bytes, the width of the Ed25519 signature a proof carries, for sizing the8/// signature, following Reticulum@1.5.0 RNS/Packet.py:403-404.9pub const signature_bytes: u16 = 64;10/// 96 bytes, a proof payload that carries the proved packet's hash ahead of the11/// signature, for sizing or recognizing the longer of the two proof payloads,12/// following Reticulum@1.5.0 RNS/Packet.py:403.13pub const explicit_bytes: u16 = packet_hash_bytes + signature_bytes;14/// 64 bytes, a proof payload that carries the signature alone, which the15/// receiver matches against a packet it is already waiting on, for sizing or16/// recognizing the shorter of the two proof payloads, following Reticulum@1.5.017/// RNS/Packet.py:404.18pub const implicit_bytes: u16 = signature_bytes;1920pub const Explicit = struct {21    packet_hash: [packet_hash_bytes]u8,22    signature: [signature_bytes]u8,23};2425pub const Implicit = struct {26    signature: [signature_bytes]u8,27};2829pub const Proof = union(enum) {30    explicit: Explicit,31    implicit: Implicit,32};3334pub const DecodeError = error{InvalidLength};35pub const EncodeError = error{OutputTooSmall};3637/// Splits a proof payload into its pieces, and its length decides the form: 9638/// bytes give a hash and a signature, and 64 give a signature, following39/// Reticulum@1.5.0 RNS/Packet.py:403-404. The call returns40/// `error.InvalidLength` for every other length.41pub fn decode(bytes: []const u8) DecodeError!Proof {42    return switch (bytes.len) {43        explicit_bytes => .{ .explicit = .{44            .packet_hash = bytes[0..packet_hash_bytes].*,45            .signature = bytes[packet_hash_bytes..explicit_bytes].*,46        } },47        implicit_bytes => .{ .implicit = .{48            .signature = bytes[0..implicit_bytes].*,49        } },50        else => error.InvalidLength,51    };52}5354pub fn encodedLength(value: Proof) u16 {55    return switch (value) {56        .explicit => explicit_bytes,57        .implicit => implicit_bytes,58    };59}6061/// Writes a built proof payload into `out` for sending and returns the bytes62/// written, following Reticulum@1.5.0 RNS/Packet.py:403-404. The call returns63/// `error.OutputTooSmall` when `out` is shorter than the payload.64pub fn encode(value: Proof, out: []u8) EncodeError![]u8 {65    const length: usize = encodedLength(value);66    if (out.len < length) return error.OutputTooSmall;67    switch (value) {68        .explicit => |explicit| {69            std.mem.copyForwards(u8, out[0..packet_hash_bytes], &explicit.packet_hash);70            std.mem.copyForwards(71                u8,72                out[packet_hash_bytes..explicit_bytes],73                &explicit.signature,74            );75        },76        .implicit => |implicit| {77            std.mem.copyForwards(u8, out[0..implicit_bytes], &implicit.signature);78        },79    }80    return out[0..length];81}8283/// Returns the first 16 bytes of a proved packet's hash as the destination for84/// addressing the proof packet sent back, following Reticulum@1.5.085/// RNS/Packet.py:381-384.86pub fn destinationHash(packet_hash: [packet_hash_bytes]u8) [16]u8 {87    return packet_hash[0..16].*;88}8990test "Reticulum@1.5.0 RNS/Packet.py:403-404 splits and joins both proof forms" {91    var explicit_raw: [explicit_bytes]u8 = undefined;92    for (&explicit_raw, 0..) |*byte, index| byte.* = @intCast(index);93    const explicit = try decode(&explicit_raw);94    var explicit_out: [explicit_bytes]u8 = undefined;95    try std.testing.expectEqualSlices(u8, &explicit_raw, try encode(explicit, &explicit_out));9697    var implicit_raw: [implicit_bytes]u8 = undefined;98    for (&implicit_raw, 0..) |*byte, index| byte.* = @intCast(index);99    const implicit = try decode(&implicit_raw);100    var implicit_out: [implicit_bytes]u8 = undefined;101    try std.testing.expectEqualSlices(u8, &implicit_raw, try encode(implicit, &implicit_out));102}103104test "Reticulum@1.5.0 RNS/Packet.py:381-384 truncates proof destinations" {105    var packet_hash: [packet_hash_bytes]u8 = undefined;106    for (&packet_hash, 0..) |*byte, index| byte.* = @intCast(index);107    try std.testing.expectEqualSlices(u8, packet_hash[0..16], &destinationHash(packet_hash));108}109110test "Reticulum@1.5.0 RNS/Packet.py:403-404 rejects other proof lengths" {111    var bytes: [explicit_bytes + 1]u8 = @splat(0);112    try std.testing.expectError(error.InvalidLength, decode(bytes[0 .. implicit_bytes - 1]));113    try std.testing.expectError(error.InvalidLength, decode(bytes[0 .. implicit_bytes + 1]));114    try std.testing.expectError(error.InvalidLength, decode(bytes[0 .. explicit_bytes - 1]));115    try std.testing.expectError(error.InvalidLength, decode(&bytes));116}

1pub const proof = @import("proof.zig");