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package chacha20_ref
import "core:crypto/_chacha20"
import "core:encoding/endian"
import "core:math/bits"
// At least with LLVM21 force_inline produces identical perf to
// manual inlining, yay.
@(private)
quarter_round :: #force_inline proc "contextless" (a, b, c, d: u32) -> (u32, u32, u32, u32) {
a, b, c, d := a, b, c, d
a += b
d ~= a
d = bits.rotate_left32(d, 16)
c += d
b ~= c
b = bits.rotate_left32(b, 12)
a += b
d ~= a
d = bits.rotate_left32(d, 8)
c += d
b ~= c
b = bits.rotate_left32(b, 7)
return a, b, c, d
}
stream_blocks :: proc(ctx: ^_chacha20.Context, dst, src: []byte, nr_blocks: int) {
// Enforce the maximum consumed keystream per IV.
_chacha20.check_counter_limit(ctx, nr_blocks)
dst, src := dst, src
x := &ctx._s
// Filippo Valsorda made an observation that only one of the column
// round depends on the counter (s12), so it is worth precomputing
// and reusing across multiple blocks. As far as I know, only Go's
// chacha implementation does this.
p1, p5, p9, p13 := quarter_round(_chacha20.SIGMA_1, x[5], x[9], x[13])
p2, p6, p10, p14 := quarter_round(_chacha20.SIGMA_2, x[6], x[10], x[14])
p3, p7, p11, p15 := quarter_round(_chacha20.SIGMA_3, x[7], x[11], x[15])
for n := 0; n < nr_blocks; n = n + 1 {
// First column round that depends on the counter
p0, p4, p8, p12 := quarter_round(_chacha20.SIGMA_0, x[4], x[8], x[12])
// First diagonal round
x0, x5, x10, x15 := quarter_round(p0, p5, p10, p15)
x1, x6, x11, x12 := quarter_round(p1, p6, p11, p12)
x2, x7, x8, x13 := quarter_round(p2, p7, p8, p13)
x3, x4, x9, x14 := quarter_round(p3, p4, p9, p14)
for i := _chacha20.ROUNDS - 2; i > 0; i = i - 2 {
x0, x4, x8, x12 = quarter_round(x0, x4, x8, x12)
x1, x5, x9, x13 = quarter_round(x1, x5, x9, x13)
x2, x6, x10, x14 = quarter_round(x2, x6, x10, x14)
x3, x7, x11, x15 = quarter_round(x3, x7, x11, x15)
x0, x5, x10, x15 = quarter_round(x0, x5, x10, x15)
x1, x6, x11, x12 = quarter_round(x1, x6, x11, x12)
x2, x7, x8, x13 = quarter_round(x2, x7, x8, x13)
x3, x4, x9, x14 = quarter_round(x3, x4, x9, x14)
}
x0 += _chacha20.SIGMA_0
x1 += _chacha20.SIGMA_1
x2 += _chacha20.SIGMA_2
x3 += _chacha20.SIGMA_3
x4 += x[4]
x5 += x[5]
x6 += x[6]
x7 += x[7]
x8 += x[8]
x9 += x[9]
x10 += x[10]
x11 += x[11]
x12 += x[12]
x13 += x[13]
x14 += x[14]
x15 += x[15]
// - The caller(s) ensure that src/dst are valid.
// - The compiler knows if the target is picky about alignment.
#no_bounds_check {
if src != nil {
endian.unchecked_put_u32le(dst[0:4], endian.unchecked_get_u32le(src[0:4]) ~ x0)
endian.unchecked_put_u32le(dst[4:8], endian.unchecked_get_u32le(src[4:8]) ~ x1)
endian.unchecked_put_u32le(dst[8:12], endian.unchecked_get_u32le(src[8:12]) ~ x2)
endian.unchecked_put_u32le(dst[12:16], endian.unchecked_get_u32le(src[12:16]) ~ x3)
endian.unchecked_put_u32le(dst[16:20], endian.unchecked_get_u32le(src[16:20]) ~ x4)
endian.unchecked_put_u32le(dst[20:24], endian.unchecked_get_u32le(src[20:24]) ~ x5)
endian.unchecked_put_u32le(dst[24:28], endian.unchecked_get_u32le(src[24:28]) ~ x6)
endian.unchecked_put_u32le(dst[28:32], endian.unchecked_get_u32le(src[28:32]) ~ x7)
endian.unchecked_put_u32le(dst[32:36], endian.unchecked_get_u32le(src[32:36]) ~ x8)
endian.unchecked_put_u32le(dst[36:40], endian.unchecked_get_u32le(src[36:40]) ~ x9)
endian.unchecked_put_u32le(
dst[40:44],
endian.unchecked_get_u32le(src[40:44]) ~ x10,
)
endian.unchecked_put_u32le(
dst[44:48],
endian.unchecked_get_u32le(src[44:48]) ~ x11,
)
endian.unchecked_put_u32le(
dst[48:52],
endian.unchecked_get_u32le(src[48:52]) ~ x12,
)
endian.unchecked_put_u32le(
dst[52:56],
endian.unchecked_get_u32le(src[52:56]) ~ x13,
)
endian.unchecked_put_u32le(
dst[56:60],
endian.unchecked_get_u32le(src[56:60]) ~ x14,
)
endian.unchecked_put_u32le(
dst[60:64],
endian.unchecked_get_u32le(src[60:64]) ~ x15,
)
src = src[_chacha20.BLOCK_SIZE:]
} else {
endian.unchecked_put_u32le(dst[0:4], x0)
endian.unchecked_put_u32le(dst[4:8], x1)
endian.unchecked_put_u32le(dst[8:12], x2)
endian.unchecked_put_u32le(dst[12:16], x3)
endian.unchecked_put_u32le(dst[16:20], x4)
endian.unchecked_put_u32le(dst[20:24], x5)
endian.unchecked_put_u32le(dst[24:28], x6)
endian.unchecked_put_u32le(dst[28:32], x7)
endian.unchecked_put_u32le(dst[32:36], x8)
endian.unchecked_put_u32le(dst[36:40], x9)
endian.unchecked_put_u32le(dst[40:44], x10)
endian.unchecked_put_u32le(dst[44:48], x11)
endian.unchecked_put_u32le(dst[48:52], x12)
endian.unchecked_put_u32le(dst[52:56], x13)
endian.unchecked_put_u32le(dst[56:60], x14)
endian.unchecked_put_u32le(dst[60:64], x15)
}
dst = dst[_chacha20.BLOCK_SIZE:]
}
// Increment the counter. Overflow checking is done upon
// entry into the routine, so a 64-bit increment safely
// covers both cases.
new_ctr := ((u64(ctx._s[13]) << 32) | u64(ctx._s[12])) + 1
x[12] = u32(new_ctr)
x[13] = u32(new_ctr >> 32)
}
}
hchacha20 :: proc "contextless" (dst, key, iv: []byte) {
x0, x1, x2, x3 := _chacha20.SIGMA_0, _chacha20.SIGMA_1, _chacha20.SIGMA_2, _chacha20.SIGMA_3
x4 := endian.unchecked_get_u32le(key[0:4])
x5 := endian.unchecked_get_u32le(key[4:8])
x6 := endian.unchecked_get_u32le(key[8:12])
x7 := endian.unchecked_get_u32le(key[12:16])
x8 := endian.unchecked_get_u32le(key[16:20])
x9 := endian.unchecked_get_u32le(key[20:24])
x10 := endian.unchecked_get_u32le(key[24:28])
x11 := endian.unchecked_get_u32le(key[28:32])
x12 := endian.unchecked_get_u32le(iv[0:4])
x13 := endian.unchecked_get_u32le(iv[4:8])
x14 := endian.unchecked_get_u32le(iv[8:12])
x15 := endian.unchecked_get_u32le(iv[12:16])
for i := _chacha20.ROUNDS; i > 0; i = i - 2 {
x0, x4, x8, x12 = quarter_round(x0, x4, x8, x12)
x1, x5, x9, x13 = quarter_round(x1, x5, x9, x13)
x2, x6, x10, x14 = quarter_round(x2, x6, x10, x14)
x3, x7, x11, x15 = quarter_round(x3, x7, x11, x15)
x0, x5, x10, x15 = quarter_round(x0, x5, x10, x15)
x1, x6, x11, x12 = quarter_round(x1, x6, x11, x12)
x2, x7, x8, x13 = quarter_round(x2, x7, x8, x13)
x3, x4, x9, x14 = quarter_round(x3, x4, x9, x14)
}
endian.unchecked_put_u32le(dst[0:4], x0)
endian.unchecked_put_u32le(dst[4:8], x1)
endian.unchecked_put_u32le(dst[8:12], x2)
endian.unchecked_put_u32le(dst[12:16], x3)
endian.unchecked_put_u32le(dst[16:20], x12)
endian.unchecked_put_u32le(dst[20:24], x13)
endian.unchecked_put_u32le(dst[24:28], x14)
endian.unchecked_put_u32le(dst[28:32], x15)
}
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