zig/std/crypto/chacha20.zig
Marc Tiehuis 87eb95f816 speed up chacha20
The main changes are:

    Unrolling the inner rounds of salsa20_wordtobyte which doubles the speed.
    Passing the slice explicitly instead of returning the array saves a copy (can optimize out in future with copy elision) and gives ~10% improvement.
    Inlining the outer loop gives ~15-20% improvement but it costs an extra 4Kb of code space. I think the tradeoff is worthwhile here.
    The other inline loops are small and can be done by the compiler if it is worthwhile.
    The rotate function replacement doesn't alter the performance from the former.

The modified throughput test I've used to benchmark is as follows. Interestingly we need to allocate memory instead of using a fixed buffer else Zig optimizes the whole thing out.

https://github.com/ziglang/zig/pull/1369#issuecomment-416456628
2018-08-27 22:55:53 -07:00

430 lines
16 KiB
Zig

// Based on public domain Supercop by Daniel J. Bernstein
const std = @import("../index.zig");
const mem = std.mem;
const endian = std.endian;
const assert = std.debug.assert;
const builtin = @import("builtin");
const QuarterRound = struct {
a: usize,
b: usize,
c: usize,
d: usize,
};
fn Rp(a: usize, b: usize, c: usize, d: usize) QuarterRound {
return QuarterRound{
.a = a,
.b = b,
.c = c,
.d = d,
};
}
// The chacha family of ciphers are based on the salsa family.
fn salsa20_wordtobyte(out: []u8, input: [16]u32) void {
assert(out.len >= 64);
var x: [16]u32 = undefined;
for (x) |_, i|
x[i] = input[i];
const rounds = comptime []QuarterRound{
Rp( 0, 4, 8,12),
Rp( 1, 5, 9,13),
Rp( 2, 6,10,14),
Rp( 3, 7,11,15),
Rp( 0, 5,10,15),
Rp( 1, 6,11,12),
Rp( 2, 7, 8,13),
Rp( 3, 4, 9,14),
};
comptime var j: usize = 0;
inline while (j < 20) : (j += 2) {
// two-round cycles
inline for (rounds) |r| {
x[r.a] +%= x[r.b]; x[r.d] = std.math.rotl(u32, x[r.d] ^ x[r.a], u32(16));
x[r.c] +%= x[r.d]; x[r.b] = std.math.rotl(u32, x[r.b] ^ x[r.c], u32(12));
x[r.a] +%= x[r.b]; x[r.d] = std.math.rotl(u32, x[r.d] ^ x[r.a], u32(8));
x[r.c] +%= x[r.d]; x[r.b] = std.math.rotl(u32, x[r.b] ^ x[r.c], u32(7));
}
}
for (x) |_, i| {
mem.writeInt(out[4 * i .. 4 * i + 4], x[i] +% input[i], builtin.Endian.Little);
}
}
fn chaCha20_internal(out: []u8, in: []const u8, key: [8]u32, counter: [4]u32) void {
var ctx: [16]u32 = undefined;
var remaining: usize = if (in.len > out.len) in.len else out.len;
var cursor: usize = 0;
const c = "expand 32-byte k";
const constant_le = []u32{
mem.readIntLE(u32, c[0..4]),
mem.readIntLE(u32, c[4..8]),
mem.readIntLE(u32, c[8..12]),
mem.readIntLE(u32, c[12..16]),
};
mem.copy(u32, ctx[0..], constant_le[0..4]);
mem.copy(u32, ctx[4..12], key[0..8]);
mem.copy(u32, ctx[12..16], counter[0..4]);
while (true) {
var buf: [64]u8 = undefined;
salsa20_wordtobyte(buf[0..], ctx);
if (remaining < 64) {
var i: usize = 0;
while (i < remaining) : (i += 1)
out[cursor + i] = in[cursor + i] ^ buf[i];
return;
}
var i: usize = 0;
while (i < 64) : (i += 1)
out[cursor + i] = in[cursor + i] ^ buf[i];
cursor += 64;
remaining -= 64;
ctx[12] += 1;
}
}
/// ChaCha20 avoids the possibility of timing attacks, as there are no branches
/// on secret key data.
///
/// in and out should be the same length.
/// counter should generally be 0 or 1
///
/// ChaCha20 is self-reversing. To decrypt just run the cipher with the same
/// counter, nonce, and key.
pub fn chaCha20IETF(out: []u8, in: []const u8, counter: u32, key: [32]u8, nonce: [12]u8) void {
assert(in.len >= out.len);
assert((in.len >> 6) + counter <= @maxValue(u32));
var k: [8]u32 = undefined;
var c: [4]u32 = undefined;
k[0] = mem.readIntLE(u32, key[0..4]);
k[1] = mem.readIntLE(u32, key[4..8]);
k[2] = mem.readIntLE(u32, key[8..12]);
k[3] = mem.readIntLE(u32, key[12..16]);
k[4] = mem.readIntLE(u32, key[16..20]);
k[5] = mem.readIntLE(u32, key[20..24]);
k[6] = mem.readIntLE(u32, key[24..28]);
k[7] = mem.readIntLE(u32, key[28..32]);
c[0] = counter;
c[1] = mem.readIntLE(u32, nonce[0..4]);
c[2] = mem.readIntLE(u32, nonce[4..8]);
c[3] = mem.readIntLE(u32, nonce[8..12]);
chaCha20_internal(out, in, k, c);
}
/// This is the original ChaCha20 before RFC 7539, which recommends using the
/// orgininal version on applications such as disk or file encryption that might
/// exceed the 256 GiB limit of the 96-bit nonce version.
pub fn chaCha20With64BitNonce(out: []u8, in: []const u8, counter: u64, key: [32]u8, nonce: [8]u8) void {
assert(in.len >= out.len);
assert(counter +% (in.len >> 6) >= counter);
var cursor: u64 = 0;
var k: [8]u32 = undefined;
var c: [4]u32 = undefined;
k[0] = mem.readIntLE(u32, key[0..4]);
k[1] = mem.readIntLE(u32, key[4..8]);
k[2] = mem.readIntLE(u32, key[8..12]);
k[3] = mem.readIntLE(u32, key[12..16]);
k[4] = mem.readIntLE(u32, key[16..20]);
k[5] = mem.readIntLE(u32, key[20..24]);
k[6] = mem.readIntLE(u32, key[24..28]);
k[7] = mem.readIntLE(u32, key[28..32]);
c[0] = @truncate(u32, counter);
c[1] = @truncate(u32, counter >> 32);
c[2] = mem.readIntLE(u32, nonce[0..4]);
c[3] = mem.readIntLE(u32, nonce[4..8]);
const block_size = (1 << 6);
const big_block = (block_size << 32);
// first partial big block
if (((@intCast(u64, @maxValue(u32) - @truncate(u32, counter)) + 1) << 6) < in.len) {
chaCha20_internal(out[cursor..big_block], in[cursor..big_block], k, c);
cursor = big_block - cursor;
c[1] += 1;
if (comptime @sizeOf(usize) > 4) {
// A big block is giant: 256 GiB, but we can avoid this limitation
var remaining_blocks: u32 = @intCast(u32, (in.len / big_block));
var i: u32 = 0;
while (remaining_blocks > 0) : (remaining_blocks -= 1) {
chaCha20_internal(out[cursor..cursor + big_block], in[cursor..cursor + big_block], k, c);
c[1] += 1; // upper 32-bit of counter, generic chaCha20_internal() doesn't
// know about this.
cursor += big_block;
}
}
}
chaCha20_internal(out[cursor..], in[cursor..], k, c);
}
// https://tools.ietf.org/html/rfc7539#section-2.4.2
test "crypto.chacha20 test vector sunscreen" {
const expected_result = []u8{
0x6e, 0x2e, 0x35, 0x9a, 0x25, 0x68, 0xf9, 0x80,
0x41, 0xba, 0x07, 0x28, 0xdd, 0x0d, 0x69, 0x81,
0xe9, 0x7e, 0x7a, 0xec, 0x1d, 0x43, 0x60, 0xc2,
0x0a, 0x27, 0xaf, 0xcc, 0xfd, 0x9f, 0xae, 0x0b,
0xf9, 0x1b, 0x65, 0xc5, 0x52, 0x47, 0x33, 0xab,
0x8f, 0x59, 0x3d, 0xab, 0xcd, 0x62, 0xb3, 0x57,
0x16, 0x39, 0xd6, 0x24, 0xe6, 0x51, 0x52, 0xab,
0x8f, 0x53, 0x0c, 0x35, 0x9f, 0x08, 0x61, 0xd8,
0x07, 0xca, 0x0d, 0xbf, 0x50, 0x0d, 0x6a, 0x61,
0x56, 0xa3, 0x8e, 0x08, 0x8a, 0x22, 0xb6, 0x5e,
0x52, 0xbc, 0x51, 0x4d, 0x16, 0xcc, 0xf8, 0x06,
0x81, 0x8c, 0xe9, 0x1a, 0xb7, 0x79, 0x37, 0x36,
0x5a, 0xf9, 0x0b, 0xbf, 0x74, 0xa3, 0x5b, 0xe6,
0xb4, 0x0b, 0x8e, 0xed, 0xf2, 0x78, 0x5e, 0x42,
0x87, 0x4d,
};
const input = "Ladies and Gentlemen of the class of '99: If I could offer you only one tip for the future, sunscreen would be it.";
var result: [114]u8 = undefined;
const key = []u8{
0, 1, 2, 3, 4, 5, 6, 7,
8, 9,10,11,12,13,14,15,
16,17,18,19,20,21,22,23,
24,25,26,27,28,29,30,31,
};
const nonce = []u8{
0, 0, 0, 0,
0, 0, 0, 0x4a,
0, 0, 0, 0,
};
chaCha20IETF(result[0..], input[0..], 1, key, nonce);
assert(mem.eql(u8, expected_result, result));
// Chacha20 is self-reversing.
var plaintext: [114]u8 = undefined;
chaCha20IETF(plaintext[0..], result[0..], 1, key, nonce);
assert(mem.compare(u8, input, plaintext) == mem.Compare.Equal);
}
// https://tools.ietf.org/html/draft-agl-tls-chacha20poly1305-04#section-7
test "crypto.chacha20 test vector 1" {
const expected_result = []u8{
0x76, 0xb8, 0xe0, 0xad, 0xa0, 0xf1, 0x3d, 0x90,
0x40, 0x5d, 0x6a, 0xe5, 0x53, 0x86, 0xbd, 0x28,
0xbd, 0xd2, 0x19, 0xb8, 0xa0, 0x8d, 0xed, 0x1a,
0xa8, 0x36, 0xef, 0xcc, 0x8b, 0x77, 0x0d, 0xc7,
0xda, 0x41, 0x59, 0x7c, 0x51, 0x57, 0x48, 0x8d,
0x77, 0x24, 0xe0, 0x3f, 0xb8, 0xd8, 0x4a, 0x37,
0x6a, 0x43, 0xb8, 0xf4, 0x15, 0x18, 0xa1, 0x1c,
0xc3, 0x87, 0xb6, 0x69, 0xb2, 0xee, 0x65, 0x86,
};
const input = []u8{
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
};
var result: [64]u8 = undefined;
const key = []u8{
0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0,
};
const nonce = []u8{0, 0, 0, 0, 0, 0, 0, 0};
chaCha20With64BitNonce(result[0..], input[0..], 0, key, nonce);
assert(mem.eql(u8, expected_result, result));
}
test "crypto.chacha20 test vector 2" {
const expected_result = []u8{
0x45, 0x40, 0xf0, 0x5a, 0x9f, 0x1f, 0xb2, 0x96,
0xd7, 0x73, 0x6e, 0x7b, 0x20, 0x8e, 0x3c, 0x96,
0xeb, 0x4f, 0xe1, 0x83, 0x46, 0x88, 0xd2, 0x60,
0x4f, 0x45, 0x09, 0x52, 0xed, 0x43, 0x2d, 0x41,
0xbb, 0xe2, 0xa0, 0xb6, 0xea, 0x75, 0x66, 0xd2,
0xa5, 0xd1, 0xe7, 0xe2, 0x0d, 0x42, 0xaf, 0x2c,
0x53, 0xd7, 0x92, 0xb1, 0xc4, 0x3f, 0xea, 0x81,
0x7e, 0x9a, 0xd2, 0x75, 0xae, 0x54, 0x69, 0x63,
};
const input = []u8{
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
};
var result: [64]u8 = undefined;
const key = []u8{
0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 1,
};
const nonce = []u8{0, 0, 0, 0, 0, 0, 0, 0};
chaCha20With64BitNonce(result[0..], input[0..], 0, key, nonce);
assert(mem.eql(u8, expected_result, result));
}
test "crypto.chacha20 test vector 3" {
const expected_result = []u8{
0xde, 0x9c, 0xba, 0x7b, 0xf3, 0xd6, 0x9e, 0xf5,
0xe7, 0x86, 0xdc, 0x63, 0x97, 0x3f, 0x65, 0x3a,
0x0b, 0x49, 0xe0, 0x15, 0xad, 0xbf, 0xf7, 0x13,
0x4f, 0xcb, 0x7d, 0xf1, 0x37, 0x82, 0x10, 0x31,
0xe8, 0x5a, 0x05, 0x02, 0x78, 0xa7, 0x08, 0x45,
0x27, 0x21, 0x4f, 0x73, 0xef, 0xc7, 0xfa, 0x5b,
0x52, 0x77, 0x06, 0x2e, 0xb7, 0xa0, 0x43, 0x3e,
0x44, 0x5f, 0x41, 0xe3,
};
const input = []u8{
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00,
};
var result: [60]u8 = undefined;
const key = []u8{
0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0,
};
const nonce = []u8{0, 0, 0, 0, 0, 0, 0, 1};
chaCha20With64BitNonce(result[0..], input[0..], 0, key, nonce);
assert(mem.eql(u8, expected_result, result));
}
test "crypto.chacha20 test vector 4" {
const expected_result = []u8{
0xef, 0x3f, 0xdf, 0xd6, 0xc6, 0x15, 0x78, 0xfb,
0xf5, 0xcf, 0x35, 0xbd, 0x3d, 0xd3, 0x3b, 0x80,
0x09, 0x63, 0x16, 0x34, 0xd2, 0x1e, 0x42, 0xac,
0x33, 0x96, 0x0b, 0xd1, 0x38, 0xe5, 0x0d, 0x32,
0x11, 0x1e, 0x4c, 0xaf, 0x23, 0x7e, 0xe5, 0x3c,
0xa8, 0xad, 0x64, 0x26, 0x19, 0x4a, 0x88, 0x54,
0x5d, 0xdc, 0x49, 0x7a, 0x0b, 0x46, 0x6e, 0x7d,
0x6b, 0xbd, 0xb0, 0x04, 0x1b, 0x2f, 0x58, 0x6b,
};
const input = []u8{
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
};
var result: [64]u8 = undefined;
const key = []u8{
0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0,
};
const nonce = []u8{1, 0, 0, 0, 0, 0, 0, 0};
chaCha20With64BitNonce(result[0..], input[0..], 0, key, nonce);
assert(mem.eql(u8, expected_result, result));
}
test "crypto.chacha20 test vector 5" {
const expected_result = []u8{
0xf7, 0x98, 0xa1, 0x89, 0xf1, 0x95, 0xe6, 0x69,
0x82, 0x10, 0x5f, 0xfb, 0x64, 0x0b, 0xb7, 0x75,
0x7f, 0x57, 0x9d, 0xa3, 0x16, 0x02, 0xfc, 0x93,
0xec, 0x01, 0xac, 0x56, 0xf8, 0x5a, 0xc3, 0xc1,
0x34, 0xa4, 0x54, 0x7b, 0x73, 0x3b, 0x46, 0x41,
0x30, 0x42, 0xc9, 0x44, 0x00, 0x49, 0x17, 0x69,
0x05, 0xd3, 0xbe, 0x59, 0xea, 0x1c, 0x53, 0xf1,
0x59, 0x16, 0x15, 0x5c, 0x2b, 0xe8, 0x24, 0x1a,
0x38, 0x00, 0x8b, 0x9a, 0x26, 0xbc, 0x35, 0x94,
0x1e, 0x24, 0x44, 0x17, 0x7c, 0x8a, 0xde, 0x66,
0x89, 0xde, 0x95, 0x26, 0x49, 0x86, 0xd9, 0x58,
0x89, 0xfb, 0x60, 0xe8, 0x46, 0x29, 0xc9, 0xbd,
0x9a, 0x5a, 0xcb, 0x1c, 0xc1, 0x18, 0xbe, 0x56,
0x3e, 0xb9, 0xb3, 0xa4, 0xa4, 0x72, 0xf8, 0x2e,
0x09, 0xa7, 0xe7, 0x78, 0x49, 0x2b, 0x56, 0x2e,
0xf7, 0x13, 0x0e, 0x88, 0xdf, 0xe0, 0x31, 0xc7,
0x9d, 0xb9, 0xd4, 0xf7, 0xc7, 0xa8, 0x99, 0x15,
0x1b, 0x9a, 0x47, 0x50, 0x32, 0xb6, 0x3f, 0xc3,
0x85, 0x24, 0x5f, 0xe0, 0x54, 0xe3, 0xdd, 0x5a,
0x97, 0xa5, 0xf5, 0x76, 0xfe, 0x06, 0x40, 0x25,
0xd3, 0xce, 0x04, 0x2c, 0x56, 0x6a, 0xb2, 0xc5,
0x07, 0xb1, 0x38, 0xdb, 0x85, 0x3e, 0x3d, 0x69,
0x59, 0x66, 0x09, 0x96, 0x54, 0x6c, 0xc9, 0xc4,
0xa6, 0xea, 0xfd, 0xc7, 0x77, 0xc0, 0x40, 0xd7,
0x0e, 0xaf, 0x46, 0xf7, 0x6d, 0xad, 0x39, 0x79,
0xe5, 0xc5, 0x36, 0x0c, 0x33, 0x17, 0x16, 0x6a,
0x1c, 0x89, 0x4c, 0x94, 0xa3, 0x71, 0x87, 0x6a,
0x94, 0xdf, 0x76, 0x28, 0xfe, 0x4e, 0xaa, 0xf2,
0xcc, 0xb2, 0x7d, 0x5a, 0xaa, 0xe0, 0xad, 0x7a,
0xd0, 0xf9, 0xd4, 0xb6, 0xad, 0x3b, 0x54, 0x09,
0x87, 0x46, 0xd4, 0x52, 0x4d, 0x38, 0x40, 0x7a,
0x6d, 0xeb, 0x3a, 0xb7, 0x8f, 0xab, 0x78, 0xc9,
};
const input = []u8{
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
};
var result: [256]u8 = undefined;
const key = []u8{
0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,
0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f,
0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17,
0x18, 0x19, 0x1a, 0x1b, 0x1c, 0x1d, 0x1e, 0x1f,
};
const nonce = []u8{
0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,
};
chaCha20With64BitNonce(result[0..], input[0..], 0, key, nonce);
assert(mem.eql(u8, expected_result, result));
}