diff --git a/mkbootimg/Android.mk b/mkbootimg/Android.mk
index a579de0..18f0ff3 100644
--- a/mkbootimg/Android.mk
+++ b/mkbootimg/Android.mk
@@ -3,6 +3,7 @@
 include $(CLEAR_VARS)
 
 LOCAL_SRC_FILES := mkbootimg.c
+LOCAL_STATIC_LIBRARIES := libmincrypt
 
 LOCAL_MODULE := mkbootimg
 
diff --git a/mkbootimg/mkbootimg.c b/mkbootimg/mkbootimg.c
index fa650cf..d803cf6 100644
--- a/mkbootimg/mkbootimg.c
+++ b/mkbootimg/mkbootimg.c
@@ -2,16 +2,16 @@
 **
 ** Copyright 2007, The Android Open Source Project
 **
-** Licensed under the Apache License, Version 2.0 (the "License"); 
-** you may not use this file except in compliance with the License. 
-** You may obtain a copy of the License at 
+** Licensed under the Apache License, Version 2.0 (the "License");
+** you may not use this file except in compliance with the License.
+** You may obtain a copy of the License at
 **
-**     http://www.apache.org/licenses/LICENSE-2.0 
+**     http://www.apache.org/licenses/LICENSE-2.0
 **
-** Unless required by applicable law or agreed to in writing, software 
-** distributed under the License is distributed on an "AS IS" BASIS, 
-** WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 
-** See the License for the specific language governing permissions and 
+** Unless required by applicable law or agreed to in writing, software
+** distributed under the License is distributed on an "AS IS" BASIS,
+** WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+** See the License for the specific language governing permissions and
 ** limitations under the License.
 */
 
@@ -21,8 +21,8 @@
 #include <unistd.h>
 #include <fcntl.h>
 #include <errno.h>
-#include <time.h>
 
+#include "mincrypt/sha.h"
 #include "bootimg.h"
 
 static void *load_file(const char *fn, unsigned *_sz)
@@ -82,7 +82,7 @@
     }
 
     count = pagesize - (itemsize & pagemask);
-    
+
     if(write(fd, padding, count) != count) {
         return -1;
     } else {
@@ -90,21 +90,10 @@
     }
 }
 
-unsigned checksum(void *_ptr, unsigned len)
-{
-    unsigned chk = 0;
-    unsigned char *ptr = _ptr;
-    while (len > 0) {
-        chk += *ptr++;
-        len--;
-    }
-    return chk;
-}
-
 int main(int argc, char **argv)
 {
     boot_img_hdr hdr;
-    
+
     char *kernel_fn = 0;
     void *kernel_data = 0;
     char *ramdisk_fn = 0;
@@ -117,12 +106,14 @@
     unsigned pagesize = 2048;
     unsigned saddr = 0;
     int fd;
-    
+    SHA_CTX ctx;
+    uint8_t* sha;
+
     argc--;
     argv++;
 
     memset(&hdr, 0, sizeof(hdr));
-    
+
     while(argc > 0){
         char *arg = argv[0];
         char *val = argv[1];
@@ -171,7 +162,7 @@
     }
 
     strcpy(hdr.name, board);
-    
+
     hdr.kernel_addr =  0x10008000;
     hdr.ramdisk_addr = 0x11000000;
     if(saddr) {
@@ -181,21 +172,21 @@
     }
     hdr.tags_addr   =  0x10000100;
     hdr.page_size = pagesize;
-    
+
     memcpy(hdr.magic, BOOT_MAGIC, BOOT_MAGIC_SIZE);
-    
+
     if(strlen(cmdline) > (BOOT_ARGS_SIZE - 1)) {
         fprintf(stderr,"error: kernel commandline too large\n");
         return 1;
     }
     strcpy((char*)hdr.cmdline, cmdline);
-    
+
     kernel_data = load_file(kernel_fn, &hdr.kernel_size);
     if(kernel_data == 0) {
         fprintf(stderr,"error: could not load kernel '%s'\n", kernel_fn);
         return 1;
     }
-    
+
     if(!strcmp(ramdisk_fn,"NONE")) {
         ramdisk_data = 0;
         hdr.ramdisk_size = 0;
@@ -215,15 +206,19 @@
         }
     }
 
-        /* put some stuff in the header to differentiate between
-         * different boot images.  SHA1 would be nicer, but this
-         * isn't for crypto grade anything, just to have a quick
-         * way to compare boot.imgs based on their first 2k
-         */
-    hdr.id[0] = (unsigned) time(0);
-    hdr.id[1] = checksum(kernel_data, hdr.kernel_size);
-    hdr.id[2] = checksum(ramdisk_data, hdr.ramdisk_size);
-    hdr.id[3] = checksum(second_data, hdr.second_size);
+    /* put a hash of the contents in the header so boot images can be
+     * differentiated based on their first 2k.
+     */
+    SHA_init(&ctx);
+    SHA_update(&ctx, kernel_data, hdr.kernel_size);
+    SHA_update(&ctx, &hdr.kernel_size, sizeof(hdr.kernel_size));
+    SHA_update(&ctx, ramdisk_data, hdr.ramdisk_size);
+    SHA_update(&ctx, &hdr.ramdisk_size, sizeof(hdr.ramdisk_size));
+    SHA_update(&ctx, second_data, hdr.second_size);
+    SHA_update(&ctx, &hdr.second_size, sizeof(hdr.second_size));
+    sha = SHA_final(&ctx);
+    memcpy(hdr.id, sha,
+           SHA_DIGEST_SIZE > sizeof(hdr.id) ? sizeof(hdr.id) : SHA_DIGEST_SIZE);
 
     fd = open(bootimg, O_CREAT | O_TRUNC | O_WRONLY, 0644);
     if(fd < 0) {
@@ -246,7 +241,7 @@
     }
 
     return 0;
-    
+
 fail:
     unlink(bootimg);
     close(fd);
@@ -254,4 +249,3 @@
             strerror(errno));
     return 1;
 }
-