diff --git a/cmds/keystore/keystore.c b/cmds/keystore/keystore.c
index ba74c7814..37155e4c4 100644
--- a/cmds/keystore/keystore.c
+++ b/cmds/keystore/keystore.c
@@ -163,19 +163,23 @@ static struct __attribute__((packed)) {
 static int8_t encrypt_blob(char *name, AES_KEY *aes_key)
 {
     uint8_t vector[AES_BLOCK_SIZE];
-    int length = blob.length;
+    int length;
     int fd;
 
     if (read(the_entropy, vector, AES_BLOCK_SIZE) != AES_BLOCK_SIZE) {
         return SYSTEM_ERROR;
     }
 
-    length += blob.value - blob.digested;
+    length = (blob.length + blob.value - blob.encrypted) % AES_BLOCK_SIZE;
+    if (length) {
+        length = AES_BLOCK_SIZE - length;
+    }
+
+    length += blob.length + blob.value - blob.digested;
     blob.length = htonl(blob.length);
     MD5(blob.digested, length, blob.digest);
 
     length += blob.digested - blob.encrypted;
-    length = (length + AES_BLOCK_SIZE - 1) / AES_BLOCK_SIZE * AES_BLOCK_SIZE;
     memcpy(vector, blob.vector, AES_BLOCK_SIZE);
     AES_cbc_encrypt(blob.encrypted, blob.encrypted, length, aes_key, vector,
                     AES_ENCRYPT);
@@ -184,11 +188,9 @@ static int8_t encrypt_blob(char *name, AES_KEY *aes_key)
     length += blob.encrypted - (uint8_t *)&blob;
 
     fd = open(".tmp", O_WRONLY | O_TRUNC | O_CREAT, S_IRUSR | S_IWUSR);
-    if (fd == -1 || write(fd, &blob, length) != length) {
-        return SYSTEM_ERROR;
-    }
+    length -= write(fd, &blob, length);
     close(fd);
-    return rename(".tmp", name) ? SYSTEM_ERROR : NO_ERROR;
+    return (length || rename(".tmp", name)) ? SYSTEM_ERROR : NO_ERROR;
 }
 
 static int8_t decrypt_blob(char *name, AES_KEY *aes_key)
@@ -210,14 +212,15 @@ static int8_t decrypt_blob(char *name, AES_KEY *aes_key)
     AES_cbc_encrypt(blob.encrypted, blob.encrypted, length, aes_key,
                     blob.vector, AES_DECRYPT);
     length -= blob.digested - blob.encrypted;
-    if (!memcmp(blob.digest, MD5(blob.digested, length, NULL),
-                MD5_DIGEST_LENGTH)) {
+    if (memcmp(blob.digest, MD5(blob.digested, length, NULL),
+               MD5_DIGEST_LENGTH)) {
         return VALUE_CORRUPTED;
     }
 
     length -= blob.value - blob.digested;
     blob.length = ntohl(blob.length);
-    return (length < blob.length) ? VALUE_CORRUPTED : NO_ERROR;
+    return (blob.length < 0 || blob.length > length) ? VALUE_CORRUPTED :
+           NO_ERROR;
 }
 
 /* Here are the actions. Each of them is a function without arguments. All