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tea.c

/* 
 * Cryptographic API.
 *
 * TEA, XTEA, and XETA crypto alogrithms
 *
 * The TEA and Xtended TEA algorithms were developed by David Wheeler 
 * and Roger Needham at the Computer Laboratory of Cambridge University.
 *
 * Due to the order of evaluation in XTEA many people have incorrectly
 * implemented it.  XETA (XTEA in the wrong order), exists for
 * compatibility with these implementations.
 *
 * Copyright (c) 2004 Aaron Grothe ajgrothe@yahoo.com
 *
 * 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/init.h>
#include <linux/module.h>
#include <linux/mm.h>
#include <asm/byteorder.h>
#include <linux/crypto.h>
#include <linux/types.h>

#define TEA_KEY_SIZE          16
#define TEA_BLOCK_SIZE        8
#define TEA_ROUNDS            32
#define TEA_DELTA       0x9e3779b9

#define XTEA_KEY_SIZE         16
#define XTEA_BLOCK_SIZE       8
#define XTEA_ROUNDS           32
#define XTEA_DELTA            0x9e3779b9

struct tea_ctx {
      u32 KEY[4];
};

struct xtea_ctx {
      u32 KEY[4];
};

static int tea_setkey(struct crypto_tfm *tfm, const u8 *in_key,
                  unsigned int key_len)
{
      struct tea_ctx *ctx = crypto_tfm_ctx(tfm);
      const __le32 *key = (const __le32 *)in_key;

      ctx->KEY[0] = le32_to_cpu(key[0]);
      ctx->KEY[1] = le32_to_cpu(key[1]);
      ctx->KEY[2] = le32_to_cpu(key[2]);
      ctx->KEY[3] = le32_to_cpu(key[3]);

      return 0; 

}

static void tea_encrypt(struct crypto_tfm *tfm, u8 *dst, const u8 *src)
{
      u32 y, z, n, sum = 0;
      u32 k0, k1, k2, k3;
      struct tea_ctx *ctx = crypto_tfm_ctx(tfm);
      const __le32 *in = (const __le32 *)src;
      __le32 *out = (__le32 *)dst;

      y = le32_to_cpu(in[0]);
      z = le32_to_cpu(in[1]);

      k0 = ctx->KEY[0];
      k1 = ctx->KEY[1];
      k2 = ctx->KEY[2];
      k3 = ctx->KEY[3];

      n = TEA_ROUNDS;

      while (n-- > 0) {
            sum += TEA_DELTA;
            y += ((z << 4) + k0) ^ (z + sum) ^ ((z >> 5) + k1);
            z += ((y << 4) + k2) ^ (y + sum) ^ ((y >> 5) + k3);
      }
      
      out[0] = cpu_to_le32(y);
      out[1] = cpu_to_le32(z);
}

static void tea_decrypt(struct crypto_tfm *tfm, u8 *dst, const u8 *src)
{
      u32 y, z, n, sum;
      u32 k0, k1, k2, k3;
      struct tea_ctx *ctx = crypto_tfm_ctx(tfm);
      const __le32 *in = (const __le32 *)src;
      __le32 *out = (__le32 *)dst;

      y = le32_to_cpu(in[0]);
      z = le32_to_cpu(in[1]);

      k0 = ctx->KEY[0];
      k1 = ctx->KEY[1];
      k2 = ctx->KEY[2];
      k3 = ctx->KEY[3];

      sum = TEA_DELTA << 5;

      n = TEA_ROUNDS;

      while (n-- > 0) {
            z -= ((y << 4) + k2) ^ (y + sum) ^ ((y >> 5) + k3);
            y -= ((z << 4) + k0) ^ (z + sum) ^ ((z >> 5) + k1);
            sum -= TEA_DELTA;
      }
      
      out[0] = cpu_to_le32(y);
      out[1] = cpu_to_le32(z);
}

static int xtea_setkey(struct crypto_tfm *tfm, const u8 *in_key,
                   unsigned int key_len)
{
      struct xtea_ctx *ctx = crypto_tfm_ctx(tfm);
      const __le32 *key = (const __le32 *)in_key;

      ctx->KEY[0] = le32_to_cpu(key[0]);
      ctx->KEY[1] = le32_to_cpu(key[1]);
      ctx->KEY[2] = le32_to_cpu(key[2]);
      ctx->KEY[3] = le32_to_cpu(key[3]);

      return 0; 

}

static void xtea_encrypt(struct crypto_tfm *tfm, u8 *dst, const u8 *src)
{
      u32 y, z, sum = 0;
      u32 limit = XTEA_DELTA * XTEA_ROUNDS;
      struct xtea_ctx *ctx = crypto_tfm_ctx(tfm);
      const __le32 *in = (const __le32 *)src;
      __le32 *out = (__le32 *)dst;

      y = le32_to_cpu(in[0]);
      z = le32_to_cpu(in[1]);

      while (sum != limit) {
            y += ((z << 4 ^ z >> 5) + z) ^ (sum + ctx->KEY[sum&3]); 
            sum += XTEA_DELTA;
            z += ((y << 4 ^ y >> 5) + y) ^ (sum + ctx->KEY[sum>>11 &3]); 
      }
      
      out[0] = cpu_to_le32(y);
      out[1] = cpu_to_le32(z);
}

static void xtea_decrypt(struct crypto_tfm *tfm, u8 *dst, const u8 *src)
{
      u32 y, z, sum;
      struct tea_ctx *ctx = crypto_tfm_ctx(tfm);
      const __le32 *in = (const __le32 *)src;
      __le32 *out = (__le32 *)dst;

      y = le32_to_cpu(in[0]);
      z = le32_to_cpu(in[1]);

      sum = XTEA_DELTA * XTEA_ROUNDS;

      while (sum) {
            z -= ((y << 4 ^ y >> 5) + y) ^ (sum + ctx->KEY[sum>>11 & 3]);
            sum -= XTEA_DELTA;
            y -= ((z << 4 ^ z >> 5) + z) ^ (sum + ctx->KEY[sum & 3]);
      }
      
      out[0] = cpu_to_le32(y);
      out[1] = cpu_to_le32(z);
}


static void xeta_encrypt(struct crypto_tfm *tfm, u8 *dst, const u8 *src)
{
      u32 y, z, sum = 0;
      u32 limit = XTEA_DELTA * XTEA_ROUNDS;
      struct xtea_ctx *ctx = crypto_tfm_ctx(tfm);
      const __le32 *in = (const __le32 *)src;
      __le32 *out = (__le32 *)dst;

      y = le32_to_cpu(in[0]);
      z = le32_to_cpu(in[1]);

      while (sum != limit) {
            y += (z << 4 ^ z >> 5) + (z ^ sum) + ctx->KEY[sum&3];
            sum += XTEA_DELTA;
            z += (y << 4 ^ y >> 5) + (y ^ sum) + ctx->KEY[sum>>11 &3];
      }
      
      out[0] = cpu_to_le32(y);
      out[1] = cpu_to_le32(z);
}

static void xeta_decrypt(struct crypto_tfm *tfm, u8 *dst, const u8 *src)
{
      u32 y, z, sum;
      struct tea_ctx *ctx = crypto_tfm_ctx(tfm);
      const __le32 *in = (const __le32 *)src;
      __le32 *out = (__le32 *)dst;

      y = le32_to_cpu(in[0]);
      z = le32_to_cpu(in[1]);

      sum = XTEA_DELTA * XTEA_ROUNDS;

      while (sum) {
            z -= (y << 4 ^ y >> 5) + (y ^ sum) + ctx->KEY[sum>>11 & 3];
            sum -= XTEA_DELTA;
            y -= (z << 4 ^ z >> 5) + (z ^ sum) + ctx->KEY[sum & 3];
      }
      
      out[0] = cpu_to_le32(y);
      out[1] = cpu_to_le32(z);
}

static struct crypto_alg tea_alg = {
      .cra_name         =     "tea",
      .cra_flags        =     CRYPTO_ALG_TYPE_CIPHER,
      .cra_blocksize          =     TEA_BLOCK_SIZE,
      .cra_ctxsize            =     sizeof (struct tea_ctx),
      .cra_alignmask          =     3,
      .cra_module       =     THIS_MODULE,
      .cra_list         =     LIST_HEAD_INIT(tea_alg.cra_list),
      .cra_u                  =     { .cipher = {
      .cia_min_keysize  =     TEA_KEY_SIZE,
      .cia_max_keysize  =     TEA_KEY_SIZE,
      .cia_setkey       =     tea_setkey,
      .cia_encrypt            =     tea_encrypt,
      .cia_decrypt            =     tea_decrypt } }
};

static struct crypto_alg xtea_alg = {
      .cra_name         =     "xtea",
      .cra_flags        =     CRYPTO_ALG_TYPE_CIPHER,
      .cra_blocksize          =     XTEA_BLOCK_SIZE,
      .cra_ctxsize            =     sizeof (struct xtea_ctx),
      .cra_alignmask          =     3,
      .cra_module       =     THIS_MODULE,
      .cra_list         =     LIST_HEAD_INIT(xtea_alg.cra_list),
      .cra_u                  =     { .cipher = {
      .cia_min_keysize  =     XTEA_KEY_SIZE,
      .cia_max_keysize  =     XTEA_KEY_SIZE,
      .cia_setkey       =     xtea_setkey,
      .cia_encrypt            =     xtea_encrypt,
      .cia_decrypt            =     xtea_decrypt } }
};

static struct crypto_alg xeta_alg = {
      .cra_name         =     "xeta",
      .cra_flags        =     CRYPTO_ALG_TYPE_CIPHER,
      .cra_blocksize          =     XTEA_BLOCK_SIZE,
      .cra_ctxsize            =     sizeof (struct xtea_ctx),
      .cra_alignmask          =     3,
      .cra_module       =     THIS_MODULE,
      .cra_list         =     LIST_HEAD_INIT(xtea_alg.cra_list),
      .cra_u                  =     { .cipher = {
      .cia_min_keysize  =     XTEA_KEY_SIZE,
      .cia_max_keysize  =     XTEA_KEY_SIZE,
      .cia_setkey       =     xtea_setkey,
      .cia_encrypt            =     xeta_encrypt,
      .cia_decrypt            =     xeta_decrypt } }
};

static int __init init(void)
{
      int ret = 0;
      
      ret = crypto_register_alg(&tea_alg);
      if (ret < 0)
            goto out;

      ret = crypto_register_alg(&xtea_alg);
      if (ret < 0) {
            crypto_unregister_alg(&tea_alg);
            goto out;
      }

      ret = crypto_register_alg(&xeta_alg);
      if (ret < 0) {
            crypto_unregister_alg(&tea_alg);
            crypto_unregister_alg(&xtea_alg);
            goto out;
      }

out:  
      return ret;
}

static void __exit fini(void)
{
      crypto_unregister_alg(&tea_alg);
      crypto_unregister_alg(&xtea_alg);
      crypto_unregister_alg(&xeta_alg);
}

MODULE_ALIAS("xtea");
MODULE_ALIAS("xeta");

module_init(init);
module_exit(fini);

MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("TEA, XTEA & XETA Cryptographic Algorithms");

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