Seqmentation fault

#include <linux/init.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <errno.h>
#include <stdio.h>
#include <string.h>

#typedef unsigned int u32;
#typedef unsigned char u8;

struct gost_ctx {
      u32 k[8];
      char k87[256],k65[256],k43[256],k21[256];
};
static unsigned char const k8[16] = { 0x1, 0xF, 0xD, 0x0, 0x5, 0x7, 0xA, 0x4, 0x9, 0x2, 0x3, 0xE, 0x6, 0xB, 0x8, 0xC };
static unsigned char const k7[16] = { 0xD, 0xB, 0x4, 0x1, 0x3, 0xF, 0x5, 0x9, 0x0, 0xA, 0xE, 0x7, 0x6, 0x8, 0x2, 0xC };
static unsigned char const k6[16] = { 0x4, 0xB, 0xA, 0x0, 0x7, 0x2, 0x1, 0xD, 0x3, 0x6, 0x8, 0x5, 0x9, 0xC, 0xF, 0xE };
static unsigned char const k5[16] = { 0x6, 0xC, 0x7, 0x1, 0x5, 0xF, 0xD, 0x8, 0x4, 0xA, 0x9, 0xE, 0x0, 0x3, 0xB, 0x2 };
static unsigned char const k4[16] = { 0x7, 0xD, 0xA, 0x1, 0x0, 0x8, 0x9, 0xF, 0xE, 0x4, 0x6, 0xC, 0xB, 0x2, 0x5, 0x3 };
static unsigned char const k3[16] = { 0x5, 0x8, 0x1, 0xD, 0xA, 0x3, 0x4, 0x2, 0xE, 0xF, 0xC, 0x7, 0x6, 0x0, 0x9, 0xB };
static unsigned char const k2[16] = { 0xE, 0xB, 0x4, 0xC, 0x6, 0xD, 0xF, 0xA, 0x2, 0x3, 0x8, 0x1, 0x0, 0x7, 0x5, 0x9 };
static unsigned char const k1[16] = { 0x4, 0xA, 0x9, 0x2, 0xD, 0x8, 0x0, 0xE, 0x6, 0xB, 0x1, 0xC, 0x7, 0xF, 0x5, 0x3 };

static int gost_setkey(struct gost_ctx *ctx, const u8 *key, unsigned int keylen){
   unsigned int *K = ctx->k;
   short i, j;
   unsigned int temp;

   for (i = 0; i < 256; i++) {
     ctx->k87 = k8[i >> 4] << 4 | k7[i & 15];
     ctx->k65 = k6[i >> 4] << 4 | k5[i & 15];
     ctx->k43 = k4[i >> 4] << 4 | k3[i & 15];
     ctx->k21 = k2[i >> 4] << 4 | k1[i & 15]; }
   for (j = 0, i = 0; i < 8; i++) {
   temp = (((u32 )key[j] << 24) | ((u32 )key[(j + 1) % keylen] << 16) |((u32 )key[(j + 2) % keylen] << 8) |((u32 )key[(j + 3) % keylen]));
   K = temp;
   j = (j + 4) % keylen;
   }
   return 0;
}

int main(void) {

struct gost_ctx *ctx;
// здесь key1 - буфер
gost_setkey(ctx,key1,keylength);

return 0;
}
-------------------------------
gcc gost.c
./a.out
-------------------------------
дает ошибка Seqmentation fault
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