213 lines
6.0 KiB
C
213 lines
6.0 KiB
C
/*
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* Salsa20: Salsa20 stream cipher algorithm
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*
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* Copyright (c) 2007 Tan Swee Heng <thesweeheng@gmail.com>
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*
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* Derived from:
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* - salsa20.c: Public domain C code by Daniel J. Bernstein <djb@cr.yp.to>
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*
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* Salsa20 is a stream cipher candidate in eSTREAM, the ECRYPT Stream
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* Cipher Project. It is designed by Daniel J. Bernstein <djb@cr.yp.to>.
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* More information about eSTREAM and Salsa20 can be found here:
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* https://www.ecrypt.eu.org/stream/
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* https://cr.yp.to/snuffle.html
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*
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* This program is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License as published by the Free
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* Software Foundation; either version 2 of the License, or (at your option)
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* any later version.
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*
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*/
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#include <asm/unaligned.h>
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#include <crypto/internal/skcipher.h>
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#include <linux/module.h>
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#define SALSA20_IV_SIZE 8
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#define SALSA20_MIN_KEY_SIZE 16
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#define SALSA20_MAX_KEY_SIZE 32
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#define SALSA20_BLOCK_SIZE 64
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struct salsa20_ctx {
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u32 initial_state[16];
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};
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static void salsa20_block(u32 *state, __le32 *stream)
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{
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u32 x[16];
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int i;
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memcpy(x, state, sizeof(x));
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for (i = 0; i < 20; i += 2) {
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x[ 4] ^= rol32((x[ 0] + x[12]), 7);
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x[ 8] ^= rol32((x[ 4] + x[ 0]), 9);
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x[12] ^= rol32((x[ 8] + x[ 4]), 13);
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x[ 0] ^= rol32((x[12] + x[ 8]), 18);
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x[ 9] ^= rol32((x[ 5] + x[ 1]), 7);
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x[13] ^= rol32((x[ 9] + x[ 5]), 9);
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x[ 1] ^= rol32((x[13] + x[ 9]), 13);
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x[ 5] ^= rol32((x[ 1] + x[13]), 18);
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x[14] ^= rol32((x[10] + x[ 6]), 7);
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x[ 2] ^= rol32((x[14] + x[10]), 9);
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x[ 6] ^= rol32((x[ 2] + x[14]), 13);
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x[10] ^= rol32((x[ 6] + x[ 2]), 18);
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x[ 3] ^= rol32((x[15] + x[11]), 7);
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x[ 7] ^= rol32((x[ 3] + x[15]), 9);
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x[11] ^= rol32((x[ 7] + x[ 3]), 13);
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x[15] ^= rol32((x[11] + x[ 7]), 18);
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x[ 1] ^= rol32((x[ 0] + x[ 3]), 7);
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x[ 2] ^= rol32((x[ 1] + x[ 0]), 9);
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x[ 3] ^= rol32((x[ 2] + x[ 1]), 13);
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x[ 0] ^= rol32((x[ 3] + x[ 2]), 18);
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x[ 6] ^= rol32((x[ 5] + x[ 4]), 7);
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x[ 7] ^= rol32((x[ 6] + x[ 5]), 9);
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x[ 4] ^= rol32((x[ 7] + x[ 6]), 13);
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x[ 5] ^= rol32((x[ 4] + x[ 7]), 18);
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x[11] ^= rol32((x[10] + x[ 9]), 7);
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x[ 8] ^= rol32((x[11] + x[10]), 9);
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x[ 9] ^= rol32((x[ 8] + x[11]), 13);
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x[10] ^= rol32((x[ 9] + x[ 8]), 18);
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x[12] ^= rol32((x[15] + x[14]), 7);
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x[13] ^= rol32((x[12] + x[15]), 9);
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x[14] ^= rol32((x[13] + x[12]), 13);
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x[15] ^= rol32((x[14] + x[13]), 18);
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}
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for (i = 0; i < 16; i++)
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stream[i] = cpu_to_le32(x[i] + state[i]);
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if (++state[8] == 0)
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state[9]++;
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}
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static void salsa20_docrypt(u32 *state, u8 *dst, const u8 *src,
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unsigned int bytes)
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{
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__le32 stream[SALSA20_BLOCK_SIZE / sizeof(__le32)];
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while (bytes >= SALSA20_BLOCK_SIZE) {
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salsa20_block(state, stream);
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crypto_xor_cpy(dst, src, (const u8 *)stream,
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SALSA20_BLOCK_SIZE);
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bytes -= SALSA20_BLOCK_SIZE;
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dst += SALSA20_BLOCK_SIZE;
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src += SALSA20_BLOCK_SIZE;
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}
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if (bytes) {
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salsa20_block(state, stream);
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crypto_xor_cpy(dst, src, (const u8 *)stream, bytes);
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}
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}
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static void salsa20_init(u32 *state, const struct salsa20_ctx *ctx,
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const u8 *iv)
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{
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memcpy(state, ctx->initial_state, sizeof(ctx->initial_state));
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state[6] = get_unaligned_le32(iv + 0);
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state[7] = get_unaligned_le32(iv + 4);
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}
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static int salsa20_setkey(struct crypto_skcipher *tfm, const u8 *key,
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unsigned int keysize)
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{
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static const char sigma[16] = "expand 32-byte k";
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static const char tau[16] = "expand 16-byte k";
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struct salsa20_ctx *ctx = crypto_skcipher_ctx(tfm);
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const char *constants;
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if (keysize != SALSA20_MIN_KEY_SIZE &&
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keysize != SALSA20_MAX_KEY_SIZE)
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return -EINVAL;
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ctx->initial_state[1] = get_unaligned_le32(key + 0);
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ctx->initial_state[2] = get_unaligned_le32(key + 4);
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ctx->initial_state[3] = get_unaligned_le32(key + 8);
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ctx->initial_state[4] = get_unaligned_le32(key + 12);
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if (keysize == 32) { /* recommended */
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key += 16;
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constants = sigma;
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} else { /* keysize == 16 */
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constants = tau;
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}
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ctx->initial_state[11] = get_unaligned_le32(key + 0);
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ctx->initial_state[12] = get_unaligned_le32(key + 4);
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ctx->initial_state[13] = get_unaligned_le32(key + 8);
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ctx->initial_state[14] = get_unaligned_le32(key + 12);
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ctx->initial_state[0] = get_unaligned_le32(constants + 0);
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ctx->initial_state[5] = get_unaligned_le32(constants + 4);
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ctx->initial_state[10] = get_unaligned_le32(constants + 8);
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ctx->initial_state[15] = get_unaligned_le32(constants + 12);
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/* space for the nonce; it will be overridden for each request */
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ctx->initial_state[6] = 0;
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ctx->initial_state[7] = 0;
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/* initial block number */
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ctx->initial_state[8] = 0;
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ctx->initial_state[9] = 0;
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return 0;
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}
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static int salsa20_crypt(struct skcipher_request *req)
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{
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struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
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const struct salsa20_ctx *ctx = crypto_skcipher_ctx(tfm);
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struct skcipher_walk walk;
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u32 state[16];
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int err;
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err = skcipher_walk_virt(&walk, req, false);
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salsa20_init(state, ctx, req->iv);
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while (walk.nbytes > 0) {
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unsigned int nbytes = walk.nbytes;
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if (nbytes < walk.total)
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nbytes = round_down(nbytes, walk.stride);
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salsa20_docrypt(state, walk.dst.virt.addr, walk.src.virt.addr,
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nbytes);
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err = skcipher_walk_done(&walk, walk.nbytes - nbytes);
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}
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return err;
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}
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static struct skcipher_alg alg = {
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.base.cra_name = "salsa20",
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.base.cra_driver_name = "salsa20-generic",
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.base.cra_priority = 100,
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.base.cra_blocksize = 1,
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.base.cra_ctxsize = sizeof(struct salsa20_ctx),
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.base.cra_module = THIS_MODULE,
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.min_keysize = SALSA20_MIN_KEY_SIZE,
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.max_keysize = SALSA20_MAX_KEY_SIZE,
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.ivsize = SALSA20_IV_SIZE,
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.chunksize = SALSA20_BLOCK_SIZE,
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.setkey = salsa20_setkey,
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.encrypt = salsa20_crypt,
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.decrypt = salsa20_crypt,
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};
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static int __init salsa20_generic_mod_init(void)
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{
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return crypto_register_skcipher(&alg);
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}
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static void __exit salsa20_generic_mod_fini(void)
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{
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crypto_unregister_skcipher(&alg);
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}
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subsys_initcall(salsa20_generic_mod_init);
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module_exit(salsa20_generic_mod_fini);
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MODULE_LICENSE("GPL");
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MODULE_DESCRIPTION ("Salsa20 stream cipher algorithm");
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MODULE_ALIAS_CRYPTO("salsa20");
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MODULE_ALIAS_CRYPTO("salsa20-generic");
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