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1b6fd3d5d1
Expose a low-level Poly1305 API which implements the
ε-almost-∆-universal (εA∆U) hash function underlying the Poly1305 MAC
and supports block-aligned inputs only.
This is needed for Adiantum hashing, which builds an εA∆U hash function
from NH and a polynomial evaluation in GF(2^{130}-5); this polynomial
evaluation is identical to the one the Poly1305 MAC does. However, the
crypto_shash Poly1305 API isn't very appropriate for this because its
calling convention assumes it is used as a MAC, with a 32-byte "one-time
key" provided for every digest.
But by design, in Adiantum hashing the performance of the polynomial
evaluation isn't nearly as critical as NH. So it suffices to just have
some C helper functions. Thus, this patch adds such functions.
Acked-by: Martin Willi <martin@strongswan.org>
Signed-off-by: Eric Biggers <ebiggers@google.com>
Acked-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
65 lines
1.7 KiB
C
65 lines
1.7 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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/*
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* Common values for the Poly1305 algorithm
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*/
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#ifndef _CRYPTO_POLY1305_H
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#define _CRYPTO_POLY1305_H
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#include <linux/types.h>
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#include <linux/crypto.h>
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#define POLY1305_BLOCK_SIZE 16
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#define POLY1305_KEY_SIZE 32
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#define POLY1305_DIGEST_SIZE 16
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struct poly1305_key {
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u32 r[5]; /* key, base 2^26 */
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};
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struct poly1305_state {
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u32 h[5]; /* accumulator, base 2^26 */
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};
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struct poly1305_desc_ctx {
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/* key */
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struct poly1305_key r;
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/* finalize key */
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u32 s[4];
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/* accumulator */
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struct poly1305_state h;
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/* partial buffer */
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u8 buf[POLY1305_BLOCK_SIZE];
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/* bytes used in partial buffer */
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unsigned int buflen;
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/* r key has been set */
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bool rset;
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/* s key has been set */
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bool sset;
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};
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/*
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* Poly1305 core functions. These implement the ε-almost-∆-universal hash
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* function underlying the Poly1305 MAC, i.e. they don't add an encrypted nonce
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* ("s key") at the end. They also only support block-aligned inputs.
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*/
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void poly1305_core_setkey(struct poly1305_key *key, const u8 *raw_key);
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static inline void poly1305_core_init(struct poly1305_state *state)
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{
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memset(state->h, 0, sizeof(state->h));
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}
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void poly1305_core_blocks(struct poly1305_state *state,
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const struct poly1305_key *key,
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const void *src, unsigned int nblocks);
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void poly1305_core_emit(const struct poly1305_state *state, void *dst);
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/* Crypto API helper functions for the Poly1305 MAC */
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int crypto_poly1305_init(struct shash_desc *desc);
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unsigned int crypto_poly1305_setdesckey(struct poly1305_desc_ctx *dctx,
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const u8 *src, unsigned int srclen);
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int crypto_poly1305_update(struct shash_desc *desc,
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const u8 *src, unsigned int srclen);
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int crypto_poly1305_final(struct shash_desc *desc, u8 *dst);
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#endif
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