096e2ec0bd
This function adds one more HSalsa key derivation to an XSalsa context that has previously been initialized. It allows multi-level cascades like the 2-level done by NaCl crypto_box.
91 lines
3.9 KiB
C
91 lines
3.9 KiB
C
/*
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* Copyright (c) 2016 Brandon Hamilton <brandon.hamilton@gmail.com>
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*
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. Neither the name of the author nor the names of his contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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#include <stdint.h>
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#include <string.h>
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#include "cryptonite_xsalsa.h"
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#include "cryptonite_align.h"
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#include "cryptonite_bitfn.h"
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/* XSalsa20 algorithm as described in https://cr.yp.to/snuffle/xsalsa-20081128.pdf */
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void cryptonite_xsalsa_init(cryptonite_salsa_context *ctx, uint8_t nb_rounds,
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uint32_t keylen, const uint8_t *key,
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uint32_t ivlen, const uint8_t *iv)
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{
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memset(ctx, 0, sizeof(*ctx));
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ctx->nb_rounds = nb_rounds;
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/* Create initial 512-bit input block:
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(x0, x5, x10, x15) is the Salsa20 constant
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(x1, x2, x3, x4, x11, x12, x13, x14) is a 256-bit key
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(x6, x7, x8, x9) is the first 128 bits of a 192-bit nonce
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*/
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cryptonite_salsa_init_core(&ctx->st, keylen, key, 8, iv);
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/* Continue initialization in a separate function that may also
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be called independently */
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cryptonite_xsalsa_derive(ctx, ivlen - 8, iv + 8);
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}
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void cryptonite_xsalsa_derive(cryptonite_salsa_context *ctx,
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uint32_t ivlen, const uint8_t *iv)
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{
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/* Finish creating initial 512-bit input block:
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(x6, x7, x8, x9) is the first 128 bits of a 192-bit nonce
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Except iv has been shifted by 64 bits so there are now only 128 bits ahead.
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*/
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ctx->st.d[ 8] += load_le32(iv + 0);
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ctx->st.d[ 9] += load_le32(iv + 4);
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/* Compute (z0, z1, . . . , z15) = doubleround ^(r/2) (x0, x1, . . . , x15) */
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block hSalsa;
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memset(&hSalsa, 0, sizeof(block));
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cryptonite_salsa_core_xor(ctx->nb_rounds, &hSalsa, &ctx->st);
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/* Build a new 512-bit input block (x′0, x′1, . . . , x′15):
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(x′0, x′5, x′10, x′15) is the Salsa20 constant
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(x′1,x′2,x′3,x′4,x′11,x′12,x′13,x′14) = (z0,z5,z10,z15,z6,z7,z8,z9)
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(x′6,x′7) is the last 64 bits of the 192-bit nonce
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(x′8, x′9) is a 64-bit block counter.
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*/
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ctx->st.d[ 1] = hSalsa.d[ 0] - ctx->st.d[ 0];
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ctx->st.d[ 2] = hSalsa.d[ 5] - ctx->st.d[ 5];
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ctx->st.d[ 3] = hSalsa.d[10] - ctx->st.d[10];
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ctx->st.d[ 4] = hSalsa.d[15] - ctx->st.d[15];
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ctx->st.d[11] = hSalsa.d[ 6] - ctx->st.d[ 6];
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ctx->st.d[12] = hSalsa.d[ 7] - ctx->st.d[ 7];
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ctx->st.d[13] = hSalsa.d[ 8] - ctx->st.d[ 8];
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ctx->st.d[14] = hSalsa.d[ 9] - ctx->st.d[ 9];
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ctx->st.d[ 6] = load_le32(iv + 8);
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ctx->st.d[ 7] = load_le32(iv + 12);
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ctx->st.d[ 8] = 0;
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ctx->st.d[ 9] = 0;
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}
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