redonkable
/
alistair23-linux
1
0
Fork 0
Code Releases Activity

crypto: chacha20-generic - add HChaCha20 library function 

Refactor the unkeyed permutation part of chacha20_block() into its own
function, then add hchacha20_block() which 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.

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>
hifive-unleashed-5.1
Eric Biggers 2018-11-16 17:26:18 -08:00 committed by Herbert Xu
parent 3d234b3313
commit dd333449d0
2 changed files with 46 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
include/crypto/chacha20.h
View File

@ -20,6 +20,8 @@ struct chacha20_ctx {
};
void chacha20_block(u32 *state, u8 *stream);
void hchacha20_block(const u32 *in, u32 *out);
void crypto_chacha20_init(u32 *state, struct chacha20_ctx *ctx, u8 *iv);
int crypto_chacha20_setkey(struct crypto_skcipher *tfm, const u8 *key,
unsigned int keysize);

50
lib/chacha20.c
View File

@ -1,5 +1,5 @@
/*
* ChaCha20 256-bit cipher algorithm, RFC7539
* The "hash function" used as the core of the ChaCha20 stream cipher (RFC7539)
*
* Copyright (C) 2015 Martin Willi
*
@ -16,14 +16,10 @@
#include <asm/unaligned.h>
#include <crypto/chacha20.h>
void chacha20_block(u32 *state, u8 *stream)
static void chacha20_permute(u32 *x)
{
u32 x[16];
int i;
for (i = 0; i < ARRAY_SIZE(x); i++)
x[i] = state[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);
@ -65,6 +61,25 @@ void chacha20_block(u32 *state, u8 *stream)
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)]);
@ -72,3 +87,26 @@ void chacha20_block(u32 *state, u8 *stream)
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);