The Keccak-f permutation.
pub fn KeccakF(comptime f: u11) typepub fn KeccakF(comptime f: u11) type {
comptime assert(f >= 200 and f <= 1600 and f % 200 == 0); // invalid bit size
const T = @Int(.unsigned, f / 25);
const Block = [25]T;
const PI = [_]u5{
10, 7, 11, 17, 18, 3, 5, 16, 8, 21, 24, 4, 15, 23, 19, 13, 12, 2, 20, 14, 22, 9, 6, 1,
};
return struct {
const Self = @This();
/// Number of bytes in the state.
pub const block_bytes = f / 8;
/// Maximum number of rounds for the given f parameter.
pub const max_rounds = 12 + 2 * math.log2(f / 25);
// Round constants
const RC = rc: {
const RC64 = [_]u64{
0x0000000000000001, 0x0000000000008082, 0x800000000000808a, 0x8000000080008000,
0x000000000000808b, 0x0000000080000001, 0x8000000080008081, 0x8000000000008009,
0x000000000000008a, 0x0000000000000088, 0x0000000080008009, 0x000000008000000a,
0x000000008000808b, 0x800000000000008b, 0x8000000000008089, 0x8000000000008003,
0x8000000000008002, 0x8000000000000080, 0x000000000000800a, 0x800000008000000a,
0x8000000080008081, 0x8000000000008080, 0x0000000080000001, 0x8000000080008008,
};
var rc: [max_rounds]T = undefined;
for (&rc, RC64[0..max_rounds]) |*t, c| t.* = @as(T, @truncate(c));
break :rc rc;
};
st: Block = @splat(0),
/// Initialize the state from a slice of bytes.
pub fn init(bytes: [block_bytes]u8) Self {
var self: Self = undefined;
inline for (&self.st, 0..) |*r, i| {
r.* = mem.readInt(T, bytes[@sizeOf(T) * i ..][0..@sizeOf(T)], .little);
}
return self;
}
/// A representation of the state as bytes. The byte order is architecture-dependent.
pub fn asBytes(self: *Self) *[block_bytes]u8 {
return mem.asBytes(&self.st);
}
/// Byte-swap the entire state if the architecture doesn't match the required endianness.
pub fn endianSwap(self: *Self) void {
for (&self.st) |*w| {
w.* = mem.littleToNative(T, w.*);
}
}
/// Set bytes starting at the beginning of the state.
pub fn setBytes(self: *Self, bytes: []const u8) void {
var i: usize = 0;
while (i + @sizeOf(T) <= bytes.len) : (i += @sizeOf(T)) {
self.st[i / @sizeOf(T)] = mem.readInt(T, bytes[i..][0..@sizeOf(T)], .little);
}
if (i < bytes.len) {
var padded: [@sizeOf(T)]u8 = @splat(0);
@memcpy(padded[0 .. bytes.len - i], bytes[i..]);
self.st[i / @sizeOf(T)] = mem.readInt(T, padded[0..], .little);
}
}
/// XOR a byte into the state at a given offset.
pub fn addByte(self: *Self, byte: u8, offset: usize) void {
const z = @sizeOf(T) * @as(math.Log2Int(T), @truncate(offset % @sizeOf(T)));
self.st[offset / @sizeOf(T)] ^= @as(T, byte) << z;
}
/// XOR bytes into the beginning of the state.
pub fn addBytes(self: *Self, bytes: []const u8) void {
var i: usize = 0;
while (i + @sizeOf(T) <= bytes.len) : (i += @sizeOf(T)) {
self.st[i / @sizeOf(T)] ^= mem.readInt(T, bytes[i..][0..@sizeOf(T)], .little);
}
if (i < bytes.len) {
var padded: [@sizeOf(T)]u8 = @splat(0);
@memcpy(padded[0 .. bytes.len - i], bytes[i..]);
self.st[i / @sizeOf(T)] ^= mem.readInt(T, padded[0..], .little);
}
}
/// Extract the first bytes of the state.
pub fn extractBytes(self: *Self, out: []u8) void {
var i: usize = 0;
while (i + @sizeOf(T) <= out.len) : (i += @sizeOf(T)) {
mem.writeInt(T, out[i..][0..@sizeOf(T)], self.st[i / @sizeOf(T)], .little);
}
if (i < out.len) {
var padded: [@sizeOf(T)]u8 = @splat(0);
mem.writeInt(T, padded[0..], self.st[i / @sizeOf(T)], .little);
@memcpy(out[i..], padded[0 .. out.len - i]);
}
}
/// XOR the first bytes of the state into a slice of bytes.
pub fn xorBytes(self: *Self, out: []u8, in: []const u8) void {
assert(out.len == in.len);
var i: usize = 0;
while (i + @sizeOf(T) <= in.len) : (i += @sizeOf(T)) {
const x = mem.readInt(T, in[i..][0..@sizeOf(T)], native_endian) ^ mem.nativeToLittle(T, self.st[i / @sizeOf(T)]);
mem.writeInt(T, out[i..][0..@sizeOf(T)], x, native_endian);
}
if (i < in.len) {
var padded: [@sizeOf(T)]u8 = @splat(0);
@memcpy(padded[0 .. in.len - i], in[i..]);
const x = mem.readInt(T, &padded, native_endian) ^ mem.nativeToLittle(T, self.st[i / @sizeOf(T)]);
mem.writeInt(T, &padded, x, native_endian);
@memcpy(out[i..], padded[0 .. in.len - i]);
}
}
/// Set the words storing the bytes of a given range to zero.
pub fn clear(self: *Self, from: usize, to: usize) void {
@memset(self.st[from / @sizeOf(T) .. (to + @sizeOf(T) - 1) / @sizeOf(T)], 0);
}
/// Clear the entire state, disabling compiler optimizations.
pub fn secureZero(self: *Self) void {
std.crypto.secureZero(T, &self.st);
}
inline fn round(self: *Self, rc: T) void {
const st = &self.st;
// theta
var t: [5]T = @splat(0);
inline for (0..5) |i| {
inline for (0..5) |j| {
t[i] ^= st[j * 5 + i];
}
}
inline for (0..5) |i| {
inline for (0..5) |j| {
st[j * 5 + i] ^= t[(i + 4) % 5] ^ math.rotl(T, t[(i + 1) % 5], 1);
}
}
// rho+pi
var last = st[1];
comptime var rotc = 0;
inline for (0..24) |i| {
const x = PI[i];
const tmp = st[x];
rotc = (rotc + i + 1) % @bitSizeOf(T);
st[x] = math.rotl(T, last, rotc);
last = tmp;
}
inline for (0..5) |i| {
inline for (0..5) |j| {
t[j] = st[i * 5 + j];
}
inline for (0..5) |j| {
st[i * 5 + j] = t[j] ^ (~t[(j + 1) % 5] & t[(j + 2) % 5]);
}
}
// iota
st[0] ^= rc;
}
/// Apply a (possibly) reduced-round permutation to the state.
pub fn permuteR(self: *Self, comptime rounds: u5) void {
var i = RC.len - rounds;
while (i < RC.len - RC.len % 3) : (i += 3) {
self.round(RC[i]);
self.round(RC[i + 1]);
self.round(RC[i + 2]);
}
while (i < RC.len) : (i += 1) {
self.round(RC[i]);
}
}
/// Apply a full-round permutation to the state.
pub fn permute(self: *Self) void {
self.permuteR(max_rounds);
}
};
}