diff options
author | Eric Biggers <ebiggers@google.com> | 2018-11-16 17:26:21 -0800 |
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committer | Herbert Xu <herbert@gondor.apana.org.au> | 2018-11-20 14:26:55 +0800 |
commit | 1ca1b917940c24ca3d1f490118c5474168622953 (patch) | |
tree | 26cde5a85d0792a8dd709a6f5316f76af8801a35 /lib/chacha20.c | |
parent | de61d7ae5d3789dcba3749a418f76613fbee8414 (diff) | |
download | linux-1ca1b917940c24ca3d1f490118c5474168622953.tar.bz2 |
crypto: chacha20-generic - refactor to allow varying number of rounds
In preparation for adding XChaCha12 support, rename/refactor
chacha20-generic to support different numbers of rounds. The
justification for needing XChaCha12 support is explained in more detail
in the patch "crypto: chacha - add XChaCha12 support".
The only difference between ChaCha{8,12,20} are the number of rounds
itself; all other parts of the algorithm are the same. Therefore,
remove the "20" from all definitions, structures, functions, files, etc.
that will be shared by all ChaCha versions.
Also make ->setkey() store the round count in the chacha_ctx (previously
chacha20_ctx). The generic code then passes the round count through to
chacha_block(). There will be a ->setkey() function for each explicitly
allowed round count; the encrypt/decrypt functions will be the same. I
decided not to do it the opposite way (same ->setkey() function for all
round counts, with different encrypt/decrypt functions) because that
would have required more boilerplate code in architecture-specific
implementations of ChaCha and XChaCha.
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Acked-by: Martin Willi <martin@strongswan.org>
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Diffstat (limited to 'lib/chacha20.c')
-rw-r--r-- | lib/chacha20.c | 112 |
1 files changed, 0 insertions, 112 deletions
diff --git a/lib/chacha20.c b/lib/chacha20.c deleted file mode 100644 index 6a484e16171d..000000000000 --- a/lib/chacha20.c +++ /dev/null @@ -1,112 +0,0 @@ -/* - * The "hash function" used as the core of the ChaCha20 stream cipher (RFC7539) - * - * Copyright (C) 2015 Martin Willi - * - * This program is free software; you can redistribute it and/or modify - * it under the terms of the GNU General Public License as published by - * the Free Software Foundation; either version 2 of the License, or - * (at your option) any later version. - */ - -#include <linux/kernel.h> -#include <linux/export.h> -#include <linux/bitops.h> -#include <linux/cryptohash.h> -#include <asm/unaligned.h> -#include <crypto/chacha20.h> - -static void chacha20_permute(u32 *x) -{ - int i; - - for (i = 0; i < 20; i += 2) { - x[0] += x[4]; x[12] = rol32(x[12] ^ x[0], 16); - x[1] += x[5]; x[13] = rol32(x[13] ^ x[1], 16); - x[2] += x[6]; x[14] = rol32(x[14] ^ x[2], 16); - x[3] += x[7]; x[15] = rol32(x[15] ^ x[3], 16); - - x[8] += x[12]; x[4] = rol32(x[4] ^ x[8], 12); - x[9] += x[13]; x[5] = rol32(x[5] ^ x[9], 12); - x[10] += x[14]; x[6] = rol32(x[6] ^ x[10], 12); - x[11] += x[15]; x[7] = rol32(x[7] ^ x[11], 12); - - x[0] += x[4]; x[12] = rol32(x[12] ^ x[0], 8); - x[1] += x[5]; x[13] = rol32(x[13] ^ x[1], 8); - x[2] += x[6]; x[14] = rol32(x[14] ^ x[2], 8); - x[3] += x[7]; x[15] = rol32(x[15] ^ x[3], 8); - - x[8] += x[12]; x[4] = rol32(x[4] ^ x[8], 7); - x[9] += x[13]; x[5] = rol32(x[5] ^ x[9], 7); - x[10] += x[14]; x[6] = rol32(x[6] ^ x[10], 7); - x[11] += x[15]; x[7] = rol32(x[7] ^ x[11], 7); - - x[0] += x[5]; x[15] = rol32(x[15] ^ x[0], 16); - x[1] += x[6]; x[12] = rol32(x[12] ^ x[1], 16); - x[2] += x[7]; x[13] = rol32(x[13] ^ x[2], 16); - x[3] += x[4]; x[14] = rol32(x[14] ^ x[3], 16); - - x[10] += x[15]; x[5] = rol32(x[5] ^ x[10], 12); - x[11] += x[12]; x[6] = rol32(x[6] ^ x[11], 12); - x[8] += x[13]; x[7] = rol32(x[7] ^ x[8], 12); - x[9] += x[14]; x[4] = rol32(x[4] ^ x[9], 12); - - x[0] += x[5]; x[15] = rol32(x[15] ^ x[0], 8); - x[1] += x[6]; x[12] = rol32(x[12] ^ x[1], 8); - x[2] += x[7]; x[13] = rol32(x[13] ^ x[2], 8); - x[3] += x[4]; x[14] = rol32(x[14] ^ x[3], 8); - - x[10] += x[15]; x[5] = rol32(x[5] ^ x[10], 7); - x[11] += x[12]; x[6] = rol32(x[6] ^ x[11], 7); - x[8] += x[13]; x[7] = rol32(x[7] ^ x[8], 7); - x[9] += x[14]; x[4] = rol32(x[4] ^ x[9], 7); - } -} - -/** - * chacha20_block - generate one keystream block and increment block counter - * @state: input state matrix (16 32-bit words) - * @stream: output keystream block (64 bytes) - * - * This is the ChaCha20 core, a function from 64-byte strings to 64-byte - * strings. The caller has already converted the endianness of the input. This - * function also handles incrementing the block counter in the input matrix. - */ -void chacha20_block(u32 *state, u8 *stream) -{ - u32 x[16]; - int i; - - memcpy(x, state, 64); - - chacha20_permute(x); - - for (i = 0; i < ARRAY_SIZE(x); i++) - put_unaligned_le32(x[i] + state[i], &stream[i * sizeof(u32)]); - - state[12]++; -} -EXPORT_SYMBOL(chacha20_block); - -/** - * hchacha20_block - abbreviated ChaCha20 core, for XChaCha20 - * @in: input state matrix (16 32-bit words) - * @out: output (8 32-bit words) - * - * HChaCha20 is the ChaCha equivalent of HSalsa20 and is an intermediate step - * towards XChaCha20 (see https://cr.yp.to/snuffle/xsalsa-20081128.pdf). - * HChaCha20 skips the final addition of the initial state, and outputs only - * certain words of the state. It should not be used for streaming directly. - */ -void hchacha20_block(const u32 *in, u32 *out) -{ - u32 x[16]; - - memcpy(x, in, 64); - - chacha20_permute(x); - - memcpy(&out[0], &x[0], 16); - memcpy(&out[4], &x[12], 16); -} -EXPORT_SYMBOL(hchacha20_block); |